error building ffi

[Mike Anderson]

On macOS Big Sur Beta I'm getting errors with:

sudo gem install ffi -v '1.12.2' --source 'https://rubygems.org/'

Here are the errors:

/usr/bin/libtool -static -o "/Library/Ruby/Gems/2.6.0/gems/ffi-1.12.2/ext/ffi_c/libffi-universal-darwin20"/.libs/libffi_convenience.a \

    "/Library/Ruby/Gems/2.6.0/gems/ffi-1.12.2/ext/ffi_c"/libffi-x86_64/.libs/libffi_convenience.a

rm -f "/Library/Ruby/Gems/2.6.0/gems/ffi-1.12.2/ext/ffi_c/libffi-universal-darwin20"/include/ffi.h

compiling AbstractMemory.c

In file included from AbstractMemory.c:47:

In file included from ./AbstractMemory.h:42:

In file included from ./Types.h:79:

./Type.h:50:5: error: unknown type name 'ffi_type'

    ffi_type* ffiType;

    ^

In file included from AbstractMemory.c:49:

In file included from ./Function.h:48:

./Call.h:93:5: error: unknown type name 'ffi_cif'

    ffi_cif cif;

    ^

In file included from AbstractMemory.c:49:

./Function.h:59:5: error: unknown type name 'ffi_type'

    ffi_type* ffiReturnType;

    ^

./Function.h:60:5: error: unknown type name 'ffi_type'

    ffi_type** ffiParameterTypes;

    ^

./Function.h:61:5: error: unknown type name 'ffi_cif'

    ffi_cif ffi_cif;

    ^

./Function.h:66:5: error: unknown type name 'ffi_abi'

    ffi_abi abi;

    ^

6 errors generated.

make: *** [AbstractMemory.o] Error 1

make failed, exit code 2