These flags in Makefile should be conditional on compiler and not just OS:
ifeq ($(UNAME),Darwin)
CFLAGS += -stdlib=libc++
CXXFLAGS += -stdlib=libc++
LDFLAGS += -stdlib=libc++
endif
Otherwise build with GCC is broken:
/opt/local/bin/gcc-mp-12 -pipe -Os -arch ppc -O2 -I ./include -stdlib=libc++ -fPIC -c -o src/cencode.o src/cencode.c
gcc-mp-12: error: unrecognized command-line option '-stdlib=libc++'
make[1]: *** [src/cencode.o] Error 1
make: *** [libsass/lib/libsass.a] Error 2
ERROR: compilation failed for package ‘sass’
These flags in Makefile should be conditional on compiler and not just OS:
Otherwise build with GCC is broken: