Compilation fails for MacOS/ARM64

[awvwgk]

This linking error occurs when cross-compiling a MacOS/ARM64 version of fpm from MacOS/x86_64.

 + $BUILD_PREFIX/bin/arm64-apple-darwin20.0.0-gfortran  -Wl,-pie -Wl,-headerpad_max_install_names -Wl,-dead_strip_dylibs -Wl,-rpath,$PREFIX/lib -L$PREFIX/lib -march=armv8.3-a -ftree-vectorize -fPIC -fno-stack-protector -O2 -pipe -isystem $PREFIX/include -fdebug-prefix-map=$SRC_DIR=/usr/local/src/conda/fpm-0.4.0 -fdebug-prefix-map=$PREFIX=/usr/local/src/conda-prefix -J build/arm64-apple-darwin20.0.0-gfortran_4605AD8986954164/fpm -I build/arm64-apple-darwin20.0.0-gfortran_4605AD8986954164/fpm  build/arm64-apple-darwin20.0.0-gfortran_4605AD8986954164/fpm/app_main.f90.o build/arm64-apple-darwin20.0.0-gfortran_4605AD8986954164/fpm/libfpm.a -o build/arm64-apple-darwin20.0.0-gfortran_4605AD8986954164/app/fpm
Undefined symbols for architecture arm64:
  "_opendir$INODE64", referenced from:
      _c_opendir in libfpm.a(src_filesystem_utilities.c.o)
  "_readdir$INODE64", referenced from:
      _c_readdir in libfpm.a(src_filesystem_utilities.c.o)
ld: symbol(s) not found for architecture arm64
collect2: error: ld returned 1 exit status
STOP 1
 <ERROR> Compilation failed for object "fpm"

It is save to assume that the current git source won't compile on native MacOS/ARM64 at the moment as well.

The additional suffix required for opendir is probably not required on MacOS/ARM64, which means we have to add another preprocessor branch for this. First, we have to identify which macro is set on MacOS/ARM64 and can be used to identify the architecture (see https://sourceforge.net/p/predef/wiki/Architectures/ for a list of architecture macros).