Fix the issue of a
clang: error: no such file or directory: 'x86_64'
error on building universal binaries on macOS.
It is also necessary to specify:
-DCMAKE_C_FLAGS="-DPNG_ARM_NEON_OPT=0"
Example CMake command:
cmake -S libpng \
-B build_libpng \
-DCMAKE_OSX_ARCHITECTURES="arm64;x86_64" \
-DCMAKE_C_FLAGS="-DPNG_ARM_NEON_OPT=0"
Signed-off-by: Cosmin Truta <ctruta@gmail.com>
Without these flags pnglibconf.c compilation fails because it
includes zlib.h -> zconf.h -> sys/types.h which is not found until we
give a correct SDK path with -isysroot flag.
Without this patch, CMAKE_C_FLAGS will be processed as a
string/filename on MSVC (e.g. when CMAKE_C_FLAGS is equal
to " /D_WIN32 /D_WINDOWS /W3") and the whole compilation fails.
