extlib: disable libpng hardware optimizations

issue #123

Author: DankRank

extlib/CMakeLists.txt

@@ -85,6 +85,7 @@ if (WITH_LIBPNG_SOURCE)
   libpng/pngwio.c libpng/pngwrite.c libpng/pngwtran.c libpng/pngwutil.c)
   target_include_directories(png PUBLIC ${CMAKE_CURRENT_BINARY_DIR}/libpng)
   target_link_libraries(png PRIVATE z math)
+  target_compile_definitions(png PRIVATE PNG_ARM_NEON_OPT=0;PNG_POWERPC_VSX_OPT=0;PNG_INTEL_SSE_OPT=0;PNG_MIPS_MSA_OPT=0;PNG_LOONGARCH_LSX_OPT=0)
   add_library(PNG::PNG ALIAS png)
   set(PNG_FOUND 1 PARENT_SCOPE)
 else()