Now that sbo packages are up I tried to add some
to my new Slackware-15.0 but most end with an
error such as this (already reinstalled glibc and gcc)

-----------------------------------
checking for gcc... gcc
checking whether the C compiler works... no
configure: error: in `/tmp/SBo/fltk-1.3.8':
configure: error: C compiler cannot create executables
See `config.log' for more details
-----------------------------------

What to do? Thanks

the config.log: (I added blank lines for readability)
-----------------------------------------------------------------------------
This file contains any messages produced by compilers while
running configure, to aid debugging if configure makes a mistake.

It was created by configure, which was
generated by GNU Autoconf 2.69. Invocation command line was

$ ./configure --prefix=/usr --sysconfdir=/etc --libdir=/usr/lib64/ --includedir=/usr/include/ --datadir=/usr/share/ --localstatedir=/var --mandir=/usr/man --enable-gl --enable-largefile --enable-shared --enable-threads --enable-xinerama --enable-xft --enable-xdbe --enable-cairo --build=x86_64-slackware-linux

## --------- ##
## Platform. ##
## --------- ##

hostname = darkstar.example.net
uname -m = x86_64
uname -r = 5.15.27
uname -s = Linux
uname -v = #1 SMP PREEMPT Tue Mar 8 18:18:11 CST 2022

/usr/bin/uname -p = Intel(R) Core(TM) i7-2630QM CPU @ 2.00GHz
/bin/uname -X = unknown

/bin/arch = x86_64
/usr/bin/arch -k = unknown
/usr/convex/getsysinfo = unknown
/usr/bin/hostinfo = unknown
/bin/machine = unknown
/usr/bin/oslevel = unknown
/bin/universe = unknown

PATH: /usr/local/sbin
PATH: /usr/local/bin
PATH: /sbin
PATH: /usr/sbin
PATH: /bin
PATH: /usr/bin

## ----------- ##
## Core tests. ##
## ----------- ##

configure:2512: checking build system type
configure:2526: result: x86_64-slackware-linux-gnu
configure:2546: checking host system type
configure:2559: result: x86_64-slackware-linux-gnu
configure:2636: checking for gcc
configure:2652: found /usr/bin/gcc
configure:2663: result: gcc
configure:2892: checking for C compiler version
configure:2901: gcc --version >&5
gcc (GCC) 11.2.0
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

configure:2912: $? = 0
configure:2901: gcc -v >&5
Reading specs from /usr/lib64/gcc/x86_64-slackware-linux/11.2.0/specs
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-slackware-linux/11.2.0/lto-wrapper
Target: x86_64-slackware-linux
Configured with: ../configure --prefix=/usr --libdir=/usr/lib64 --mandir=/usr/man --infodir=/usr/info --enable-shared --enable-bootstrap --enable-languages=ada,brig,c,c++,d,fortran,go,lto,objc,obj-c++ --enable-threads=posix --enable-checking=release --enable-objc-gc --with-system-zlib --enable-libstdcxx-dual-abi --with-default-libstdcxx-abi=new --disable-libstdcxx-pch --disable-libunwind-exceptions --enable-__cxa_atexit --disable-libssp --enable-gnu-unique-object --enable-plugin --enable-lto --disable-install-libiberty --disable-werror --with-gnu-ld --with-isl --verbose --with-arch-directory=amd64 --disable-gtktest --enable-clocale=gnu --disable-multilib --target=x86_64-slackware-linux --build=x86_64-slackware-linux --host=x86_64-slackware-linux
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.2.0 (GCC)
configure:2912: $? = 0
configure:2901: gcc -V >&5
gcc: error: unrecognized command-line option '-V'
gcc: fatal error: no input files
compilation terminated.

configure:2912: $? = 1
configure:2901: gcc -qversion >&5
gcc: error: unrecognized command-line option '-qversion'; did you mean '--version'?
gcc: fatal error: no input files
compilation terminated.

configure:2912: $? = 1
configure:2932: checking whether the C compiler works
configure:2954: gcc -O2 -fPIC conftest.c >&5
gcc: fatal error: cannot execute 'as': execvp: No such file or directory
compilation terminated.

configure:2958: $? = 1
configure:2996: result: no
configure: failed program was:
| /* confdefs.h */
| #define PACKAGE_NAME ""
| #define PACKAGE_TARNAME ""
| #define PACKAGE_VERSION ""
| #define PACKAGE_STRING ""
| #define PACKAGE_BUGREPORT ""
| #define PACKAGE_URL ""
| /* end confdefs.h. */
|
| int
| main ()
| {
|
| ;
| return 0;
| }
configure:3001: error: in `/tmp/SBo/fltk-1.3.8':
configure:3003: error: C compiler cannot create executables
See `config.log' for more details

## ---------------- ##
## Cache variables. ##
## ---------------- ##

ac_cv_build=x86_64-slackware-linux-gnu
ac_cv_env_CCC_set=
ac_cv_env_CCC_value=
ac_cv_env_CC_set=
ac_cv_env_CC_value=
ac_cv_env_CFLAGS_set=set
ac_cv_env_CFLAGS_value='-O2 -fPIC'
ac_cv_env_CPPFLAGS_set=
ac_cv_env_CPPFLAGS_value=
ac_cv_env_CPP_set=
ac_cv_env_CPP_value=
ac_cv_env_CXXFLAGS_set=set
ac_cv_env_CXXFLAGS_value='-O2 -fPIC'
ac_cv_env_CXX_set=
ac_cv_env_CXX_value=
ac_cv_env_LDFLAGS_set=
ac_cv_env_LDFLAGS_value=
ac_cv_env_LIBS_set=
ac_cv_env_LIBS_value=
ac_cv_env_XMKMF_set=
ac_cv_env_XMKMF_value=
ac_cv_env_build_alias_set=set
ac_cv_env_build_alias_value=x86_64-slackware-linux
ac_cv_env_host_alias_set=
ac_cv_env_host_alias_value=
ac_cv_env_target_alias_set=
ac_cv_env_target_alias_value=
ac_cv_host=x86_64-slackware-linux-gnu
ac_cv_prog_ac_ct_CC=gcc

## ----------------- ##
## Output variables. ##
## ----------------- ##

AR=''
ARCHFLAGS=''
AUDIOLIBS=''
BINARY_DIR=''
CAIRODIR=''
CAIRODSONAME=''
CAIROFLAGS=''
CAIROLIBBASENAME=''
CAIROLIBNAME=''
CAIROLIBS=''
CAT1EXT=''
CAT3EXT=''
CAT6EXT=''
CC='gcc'
CFLAGS='-O2 -fPIC'
CPP=''
CPPFLAGS=''
CXX=''
CXXFLAGS='-O2 -fPIC'
DEFS=''
DOXYDOC=''
DSOCOMMAND=''
DSOFLAGS=''
DSOLINK=''
DSONAME=''
ECHO_C=''
ECHO_N='-n'
ECHO_T=''
EGREP=''
EXEEXT=''
FLDSONAME=''
FLLIBBASENAME=''
FLLIBNAME=''
FLTKCAIROOPTION=''
FLTK_VERSION=''
FLTK_VERSION_MAJOR=''
FLTK_VERSION_MINOR=''
FLTK_VERSION_PATCH=''
FLUID=''
FLUID_BUILD=''
FL_ABI_VERSION=''
FL_DSO_VERSION=''
FTCONFIG=''
GLDEMOS=''
GLDSONAME=''
GLLIBBASENAME=''
GLLIBNAME=''
GLLIBS=''
GREP=''
GROFF=''
HLINKS=''
IMAGELIBS=''
IMGDSONAME=''
IMGLIBBASENAME=''
IMGLIBNAME=''
INSTALL_DATA=''
INSTALL_DESKTOP=''
INSTALL_PROGRAM=''
INSTALL_SCRIPT=''
JPEG=''
JPEGINC=''
LARGEFILE=''
LDFLAGS=''
LIBBASENAME=''
LIBCOMMAND=''
LIBEXT=''
LIBNAME=''
LIBOBJS=''
LIBS=''
LINKFLTK=''
LINKFLTKCAIRO=''
LINKFLTKFORMS=''
LINKFLTKGL=''
LINKFLTKIMG=''
LINKSHARED=''
LTLIBOBJS=''
MAKEDEPEND=''
NROFF=''
OBJEXT=''
OPTIM=''
OSX_ONLY=''
PACKAGE_BUGREPORT=''
PACKAGE_NAME=''
PACKAGE_STRING=''
PACKAGE_TARNAME=''
PACKAGE_URL=''
PACKAGE_VERSION=''
PATH_SEPARATOR=':'
PKGCONFIG=''
PNG=''
PNGINC=''
PTHREAD_FLAGS=''
RANLIB=''
RC=''
SHAREDSUFFIX=''
SHELL='/bin/sh'
STATICIMAGELIBS=''
THREADS=''
UNINSTALL_DESKTOP=''
USEMMFILES=''
XMKMF=''
XPROP=''
X_CFLAGS=''
X_EXTRA_LIBS=''
X_LIBS=''
X_PRE_LIBS=''
ZLIB=''
ZLIBINC=''
ac_ct_CC='gcc'
ac_ct_CXX=''
bindir='${exec_prefix}/bin'
build='x86_64-slackware-linux-gnu'
build_alias='x86_64-slackware-linux'
build_cpu='x86_64'
build_os='linux-gnu'
build_vendor='slackware'
datadir='/usr/share'
datarootdir='${prefix}/share'
docdir='${datarootdir}/doc/${PACKAGE}'
dvidir='${docdir}'
exec_prefix='NONE'
host='x86_64-slackware-linux-gnu'
host_alias=''
host_cpu='x86_64'
host_os='linux-gnu'
host_vendor='slackware'
htmldir='${docdir}'
includedir='/usr/include'
infodir='${datarootdir}/info'
libdir='/usr/lib64'
libexecdir='${exec_prefix}/libexec'
localedir='${datarootdir}/locale'
localstatedir='/var'
mandir='/usr/man'
oldincludedir='/usr/include'
pdfdir='${docdir}'
prefix='/usr'
program_transform_name='s,x,x,'
psdir='${docdir}'
runstatedir='${localstatedir}/run'
sbindir='${exec_prefix}/sbin'
sharedstatedir='${prefix}/com'
sysconfdir='/etc'
target_alias=''

## ----------- ##
## confdefs.h. ##
## ----------- ##

/* confdefs.h */
#define PACKAGE_NAME ""
#define PACKAGE_TARNAME ""
#define PACKAGE_VERSION ""
#define PACKAGE_STRING ""
#define PACKAGE_BUGREPORT ""
#define PACKAGE_URL ""

configure: exit 77