configure: only append -fanalyzer when building with gcc

[jchzhou]

Anaconda fails to build with clang because the compiler doesn't recognize -fanalyzer (introduced experimentally in #3482 to supplement cppcheck). Instead, check the $CC and only append -fanalyzer when building with GCC.

[M4rtinK]

/kickstart-test --testtype smoke

[M4rtinK]

I looked a bit into this & noticed that the -fanalyzer flag actually does not seem to be used during the build ? At least when running make -f ./Makefile.am container-rpms-scratch I get this logged about CFLAGS in the output:

+ CFLAGS='-O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1  -m64 -march=x86-64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -mtls-dialect=gnu2 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer '
+ export CFLAGS
+ CXXFLAGS='-O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1  -m64 -march=x86-64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -mtls-dialect=gnu2 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer '
+ export CXXFLAGS
+ FFLAGS='-O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1  -m64 -march=x86-64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -mtls-dialect=gnu2 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -I/usr/lib64/gfortran/modules '
+ export FFLAGS
+ FCFLAGS='-O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1  -m64 -march=x86-64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -mtls-dialect=gnu2 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -I/usr/lib64/gfortran/modules '
+ export FCFLAGS

(The output is the same, as it should be, with our without this PR.)

The documentation says that -fanalyzer effectively enables a bunch of options, but I don't see even those. Weird. :P

[M4rtinK]

Also I've found this article:

https://developers.redhat.com/articles/2021/07/28/write-toolchain-agnostic-rpm-spec-files-gcc-and-clang#toolchain_specific_changes

Which mentions:

As implemented in redhat-rpm-macros, the %toolchain macro always evaluates to either "gcc" or "clang." Note that one cannot generally check $CC the same way, because that variable might point to an obscure binary in cross-compilation scenarios.

The article suggests using the %toolchain macro instead of checking $CC, but given we have this defined in configure.ac that might not be that simple. Also I' not really sure Anaconda is usually affected/used in cross-compilation scenarios (IIRC all Koji/BREW) builds should happen on not just the target architecture but even on real hardware), so this might be moot.