depends: `libevent` build fails when `C{C,XX}` are provided #30439

$ make -C depends libevent HOST=x86_64-apple-darwin CC=clang CXX=clang++
make: Entering directory '/home/hebasto/git/bitcoin/depends'
Configuring libevent...
-- The C compiler identification is Clang 16.0.6
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - failed
-- Check for working C compiler: /usr/bin/clang-16
-- Check for working C compiler: /usr/bin/clang-16 - broken
CMake Error at /usr/share/cmake-3.27/Modules/CMakeTestCCompiler.cmake:67 (message):
  The C compiler

    "/usr/bin/clang-16"

  is not able to compile a simple test program.

  It fails with the following output:

    Change Dir: '/home/hebasto/git/bitcoin/depends/work/build/x86_64-apple-darwin/libevent/2.1.12-stable-a0bf1cb6f39/build/CMakeFiles/CMakeScratch/TryCompile-Y4dUBb'
    
    Run Build Command(s): /usr/bin/cmake -E env VERBOSE=1 /usr/bin/gmake -f Makefile cmTC_8ee7e/fast
    gmake[1]: Entering directory '/home/hebasto/git/bitcoin/depends/work/build/x86_64-apple-darwin/libevent/2.1.12-stable-a0bf1cb6f39/build/CMakeFiles/CMakeScratch/TryCompile-Y4dUBb'
    /usr/bin/gmake  -f CMakeFiles/cmTC_8ee7e.dir/build.make CMakeFiles/cmTC_8ee7e.dir/build
    gmake[2]: Entering directory '/home/hebasto/git/bitcoin/depends/work/build/x86_64-apple-darwin/libevent/2.1.12-stable-a0bf1cb6f39/build/CMakeFiles/CMakeScratch/TryCompile-Y4dUBb'
    Building C object CMakeFiles/cmTC_8ee7e.dir/testCCompiler.c.o
    /usr/bin/clang-16 --target=x86_64-apple-darwin   -I/home/hebasto/git/bitcoin/depends/x86_64-apple-darwin/include -D_FORTIFY_SOURCE=3 -pipe -std=c11 -mmacos-version-min=11.0 -mlinker-version=711 -O2  -fPIE -MD -MT CMakeFiles/cmTC_8ee7e.dir/testCCompiler.c.o -MF CMakeFiles/cmTC_8ee7e.dir/testCCompiler.c.o.d -o CMakeFiles/cmTC_8ee7e.dir/testCCompiler.c.o -c /home/hebasto/git/bitcoin/depends/work/build/x86_64-apple-darwin/libevent/2.1.12-stable-a0bf1cb6f39/build/CMakeFiles/CMakeScratch/TryCompile-Y4dUBb/testCCompiler.c
    Linking C executable cmTC_8ee7e
    /usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_8ee7e.dir/link.txt --verbose=1
    /usr/bin/clang-16 --target=x86_64-apple-darwin -I/home/hebasto/git/bitcoin/depends/x86_64-apple-darwin/include -D_FORTIFY_SOURCE=3 -pipe -std=c11 -mmacos-version-min=11.0 -mlinker-version=711 -O2  -Wl,-headerpad_max_install_names -Wl,-platform_version,macos,11.0,14.0 -Wl,-no_adhoc_codesign -fuse-ld=lld  -L/home/hebasto/git/bitcoin/depends/x86_64-apple-darwin/lib  CMakeFiles/cmTC_8ee7e.dir/testCCompiler.c.o -o cmTC_8ee7e 
    ld64.lld: error: library not found for -lSystem
    clang: error: linker command failed with exit code 1 (use -v to see invocation)
    gmake[2]: *** [CMakeFiles/cmTC_8ee7e.dir/build.make:100: cmTC_8ee7e] Error 1
    gmake[2]: Leaving directory '/home/hebasto/git/bitcoin/depends/work/build/x86_64-apple-darwin/libevent/2.1.12-stable-a0bf1cb6f39/build/CMakeFiles/CMakeScratch/TryCompile-Y4dUBb'
    gmake[1]: *** [Makefile:127: cmTC_8ee7e/fast] Error 2
    gmake[1]: Leaving directory '/home/hebasto/git/bitcoin/depends/work/build/x86_64-apple-darwin/libevent/2.1.12-stable-a0bf1cb6f39/build/CMakeFiles/CMakeScratch/TryCompile-Y4dUBb'
    
    

  

  CMake will not be able to correctly generate this project.
Call Stack (most recent call first):
  CMakeLists.txt:47 (project)


-- Configuring incomplete, errors occurred!
make: *** [funcs.mk:302: /home/hebasto/git/bitcoin/depends/x86_64-apple-darwin/.libevent_stamp_configured] Error 1
make: Leaving directory '/home/hebasto/git/bitcoin/depends'

Overriding those variables when cross-compiling for macOS isn't currently supported.

IIRC we also settled on the minimum clang for macOS being 18, so the Clang you're using (16), is likely too old.

Note that this is also not libevent specific. It's just that it happens to be the first thing compiled in depends.