configure: provide more context on failed ./configure.py run
configure: provide more context on failed ./configure.py run

If the configuration step failed, it used to only inform that
it must be due to the wrong GCC version, which can be misleading.
For instance, trying to compile on clang with incorrect flags
also resulted in an "wrong GCC version" message.
Now, the message is more generic, but it also prints the stderr
output from the miscompilation, which may help pinpoint the problem:

$ ./configure.py --mode release --cflags='-fhello -fcolor-diagnostics -mllvm -opt-bisect-limit=10000' --compiler=clang++ --c-compiler=clang
Note: neither lld nor gold found; using default system linker
Compilation failed: clang++ -x c++ -o build/tmp/tmp1177gojf /home/sarna/repo/scylla/build/tmp/tmp_u3voys6 -fhello -fcolor-diagnostics -mllvm -opt-bisect-limit=10000 []

// clang pretends to be gcc (defined __GNUC__), so we
// must check it first
\#ifdef __clang__

\#if __clang_major__ < 10
    #error "MAJOR"
\#endif

\#elif defined(__GNUC__)

\#if __GNUC__ < 10
    #error "MAJOR"
\#elif __GNUC__ == 10
    #if __GNUC_MINOR__ < 1
        #error "MINOR"
    #elif __GNUC_MINOR__ == 1
        #if __GNUC_PATCHLEVEL__ < 1
            #error "PATCHLEVEL"
        #endif
    #endif
\#endif

\#else

\#error "Unrecognized compiler"

\#endif

int main() { return 0; }

clang-11: error: unknown argument: '-fhello'
distcc[4085341] ERROR: compile (null) on localhost failed

Wrong compiler version or incorrect flags. Scylla needs GCC >= 10.1.1 with coroutines (-fcoroutines) or clang >= 10.0.0 to compile.

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla