sagittarius build error (ffi)

out.txt

Scanning dependencies of target sagittarius--ffi
[ 41%] Building C object build/ext/ffi/CMakeFiles/sagittarius--ffi.dir/sagittarius-ffi.c.o
[ 41%] Building C object build/ext/ffi/CMakeFiles/sagittarius--ffi.dir/ffi_stub.c.o
Linking C shared module ../../sagittarius--ffi.so
Undefined symbols for architecture x86_64:
  "_ffi_call", referenced from:
      _internal_ffi_call in sagittarius-ffi.c.o
  "_ffi_prep_cif_machdep", referenced from:
      _ffi_prep_cif in liblibffi.a(prep_cif.c.o)
  "_ffi_prep_closure_loc", referenced from:
      _prep_method_handler in sagittarius-ffi.c.o
      _ffi_prep_closure in liblibffi.a(prep_cif.c.o)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [build/sagittarius--ffi.so] Error 1
make[1]: *** [build/ext/ffi/CMakeFiles/sagittarius--ffi.dir/all] Error 2
make: *** [all] Error 2

system.c.diff

diff --git a/src/os/posix/system.c b/src/os/posix/system.c
index 9217049..0468c30 100755
--- a/src/os/posix/system.c
+++ b/src/os/posix/system.c
@@ -65,7 +65,12 @@
 #include <sagittarius/number.h>
 #include <sagittarius/bytevector.h>
 
+#if 1
+#include <crt_externs.h>
+#define environ (*_NSGetEnviron())
+#else
 extern char** environ;
+#endif
 
 /* os dependent values */
 const SgChar* Sg_NativeFileSeparator()