[libcxx] Make it possible to test static builds of libc++ on OSX

[rmaprath]

Summary

Being used to doing static builds and being a complete noob to OSX, this really confused me.

Currently if you build libc++ (in-tree) like so:

-DLIBCXX_ENABLE_SHARED=OFF -DLIBCXXABI_ENABLE_SHARED=OFF -DLIBUNWIND_ENABLE_SHARED=OFF

The libc++ test runs will fail due to missing symbols corresponding to libc++abi. This patch should fix it.

[EricWF]

Is this still needed?

[rmaprath]

Looks like I'm the only one interested in this - abandoning.

test/libcxx/test/target_info.py

     def allow_cxxabi_link(self):
         # FIXME: PR27405
         # libc++ *should* export all of the symbols found in libc++abi on OS X.
         # For this reason LibcxxConfiguration will not link libc++abi in OS X.
         # However __cxa_throw_bad_new_array_length doesn't get exported into
         # libc++ yet so we still need to explicitly link libc++abi when testing
         # libc++abi
         # See PR22654.
-        if(self.full_config.get_lit_conf('name', '') == 'libc++abi'):
+        lit_conf_name = self.full_config.get_lit_conf('name', '')
+        if(lit_conf_name == 'libc++abi'):
+            return True
+        # Needs explicit linking of libc++abi for static libc++ builds
+        if(lit_conf_name == 'libc++' and
+           not self.full_config.get_lit_bool('enable_shared', True)):
             return True
         # Don't link libc++abi explicitly on OS X because the symbols
         # should be available in libc++ directly.
         return False
 
     def add_sanitizer_features(self, sanitizer_type, features):
         if san == 'Undefined':
             features.add('sanitizer-new-delete')