llgo build fails due to something with libffi and closures

[thakkar...@gmail.com]

Hello

I'm trying to install llgo locally, and everything till the last step works fine. Towards the end, build fails with this message:

make[2]: *** [tools/llgo/libffi-prefix/src/libffi-stamp/libffi-build] Error 1
make[1]: *** [tools/llgo/CMakeFiles/libffi.dir/all] Error 2
make: *** [all] Error 2

On looking at the "llvm-build/tools/llgo/libffi-prefix/src/libffi-stamp/libffi-build-err.log" file, I see this:

```
cat: /Users/parth/Projects/progsynth/llgo/llvm/tools/llgo/third_party/gofrontend/libffi/../gcc/BASE-VER: No such file or directory
/bin/sh: /Users/parth/Projects/progsynth/llgo/llvm/tools/llgo/third_party/gofrontend/libffi/../libtool-ldflags: No such file or directory
ld: warning: could not create compact unwind for _ffi_call_unix64: does not use RBP or RSP based frame
Undefined symbols for architecture x86_64:
"_ffi_prep_raw_closure_loc", referenced from:
_ffi_prep_raw_closure in raw_api.o
ld: symbol(s) not found for architecture x86_64
clang-8: error: linker command failed with exit code 1 (use -v to see invocation)
make[5]: *** [libffi.la] Error 1
make[4]: *** [all-recursive] Error 1
make[3]: *** [all] Error 2
```

On grepping through the source code, I do see the existance of ffi_prep_raw_closure_loc in the same file as ffi_pre_raw_closure. So I'm not sure what's going on here. Can someone help me out here?

Regards
Parth