[clang] build broken "gcc: No such file or directory"

[peppergrayxyz]

The build using clang fails with an error while calling gcc

$ make
Note: Building without setproctitle() support.
      Install libbsd-devel (RPM) / libbsd-dev (DEB) to fix.
Note: Building with amdgpu_plugin.
Warn: Externally managed python environment
Consider using PIP_BREAK_SYSTEM_PACKAGES=1
  GEN      .gitid
  GEN      criu/include/version.h
  DEP      images/stats.pb-c.d
make[1]: gcc: No such file or directory

...

The missing setproctitle() support also originiates from this bug:

$ make SHELL='sh -x'

...

+ sh -c $'echo "#include <bsd/string.h>int main(void){\treturn 0;}" | gcc -O2 -g   -Wall -Wformat-security -Wdeclaration-after-statement -Wstrict-prototypes -Wno-dangling-pointer -Wno-unknown-warning-option -Werror -DCONFIG_AARCH64 -D_FILE_OFFSET_BITS=64 -D_LARGEFILE64_SOURCE -D_GNU_SOURCE -iquote include/   -x c - -lbsd -o /dev/null > /dev/null 2>&1 && echo true || echo false'
Note: Building without setproctitle() support.
      Install libbsd-devel (RPM) / libbsd-dev (DEB) to fix.

The issue is hidden from CI because the docker images have clang and gcc installed and therefore silently fall back to using gcc:

$ make -C scripts/ci alpine CLANG=1

...

+ LOCAL_COMPILE_FLAGS=("V=1")
+ gcc --version
+ make CC=gcc -j4 V=1
gcc (Alpine 15.2.0) 15.2.0

...

protoc --proto_path=images/ --c_out=images/ images/timer.proto
gcc -M -MT images/creds.pb-c.d -MT images/creds.pb-c.o -O2 -g   -Wall -Wformat-security -Wdeclaration-after-statement -Wstrict-prototypes -Wno-dangling-pointer -Wno-unknown-warning-option -Werror -DCONFIG_X86_64 -D_FILE_OFFSET_BITS=64 -D_LARGEFILE64_SOURCE -D_GNU_SOURCE -DCONFIG_GNUTLS -DCONFIG_HAS_NFTABLES_LIB_API_1 -DCONFIG_COMPAT -iquote include/ -DCONFIG_GNUTLS -DCONFIG_HAS_NFTABLES_LIB_API_1 -DCONFIG_COMPAT -iquote images/ images/creds.pb-c.c -o images/creds.pb-c.d

...