devel/libffi: fix build with lld 17

As reported in bug 273753#c12, devel/libffi fails to link with lld 17,
at least on i386:

libtool: link: cc -shared -fPIC -DPIC src/.libs/prep_cif.o src/.libs/types.o src/.libs/raw_api.o src/.libs/java_raw_api.o src/.libs/closures.o src/.libs/tramp.o src/x86/.libs/ffi.o src/x86/.libs/sysv.o -O2 -fstack-protector-strong -Wl,--version-script -Wl,libffi.map -fstack-protector-strong -Wl,-soname -Wl,libffi.so.8 -o .libs/libffi.so.8.1.2
ld: error: version script assignment of 'LIBFFI_BASE_8.0' to symbol 'ffi_java_raw_call' failed: symbol not defined
ld: error: version script assignment of 'LIBFFI_CLOSURE_8.0' to symbol 'ffi_prep_java_raw_closure' failed: symbol not defined
ld: error: version script assignment of 'LIBFFI_CLOSURE_8.0' to symbol 'ffi_prep_java_raw_closure_loc' failed: symbol not defined
cc: error: linker command failed with exit code 1 (use -v to see invocation)

This is because the symbols it complains about are not implemented on
i386, due to the FFI_NATIVE_RAW_API define being nonzero.

Fix it by adding more #if statements to libffi.map.in.

PR: 274056
Approved by: kbowling (maintainer)
MFH: 2023Q3