Fix annoying warning about -fvisibility-inlines-hidden being passed to C files with GCC.

[ActuallyaDeviloper]

When compiling with GCC (not Clang) in Make or Ninja, I noticed the following annoying warning spam:

cc1: warning: command-line option '-fvisibility-inlines-hidden' is valid for C++/ObjC++ but not for C

Apparently this flag is only for C++. (Source: https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Dialect-Options.html, where this option is listed at "command-line options that are only meaningful for C++ programs".)

The solution: Only pass this flag to the C++ compiler.

To reproduce:

Details

Reproduce by creating a premake5.lua

workspace "Repro"
	configurations { "Debug" }
	location "build/%{_ACTION}"
project "Repro"
	kind "StaticLib"
	language "C"
	inlinesvisibility "Hidden"
	files { "main.c" }

compiling a main.c

int f(void) { return 0; }

and compile with premake5 gmake && cd build/gmake && make or the equivalent ninja backend.

AI disclosure: The fix was suggested by Claude Opus 5.5. I reviewed the code and created this pull request.

[nickclark2016]

LGTM. Appreciate the AI disclosure :)