ggml : fix undefined reference to std::filesystem(#10978)

[Clauszy]

add link library stdc++fs for ggml.

[max-krasnyansky]

This is an issue with quite old GCC and Clang.
You should probably just upgrade at this point

[kou]

This is needless for recent GCC:

Suggested change

	if (CMAKE_CXX_COMPILER_ID MATCHES "GNU")
	if (CMAKE_CXX_COMPILER_ID MATCHES "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS "9")

FYI: We need c++fs (not stdc++fs) for Clang < 8 ((CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS "8")).

[slaren]

This issue is going to keep popping up as we start using std::filesystem in other components, e.g. #11013 uses it in the common library. I would suggest upgrading the version of gcc, and if that's absolutely not possible, find a workaround that does not require modifying the build files, e.g. maybe by setting LDFLAGS.