Re-add ReadDir interception on macOS

This was disabled due to issues with address sanitizer, which appear to no longer
exist. The effects of intercepting readdir are an important part of the test
framework shim, so disabling that makes some tests unreliable. It would be better
to disable address sanitizer in CI where it is found to be an issue rather than
disable readdir interception.

Author: charles-lunarg

tests/framework/shim/unix_shim.cpp

@@ -397,8 +397,7 @@ struct Interposer {
 };
 
 __attribute__((used)) static Interposer _interpose_opendir MACOS_ATTRIB = {VOIDP_CAST(my_opendir), VOIDP_CAST(opendir)};
-// don't intercept readdir as it crashes when using ASAN with macOS
-// __attribute__((used)) static Interposer _interpose_readdir MACOS_ATTRIB = {VOIDP_CAST(my_readdir), VOIDP_CAST(readdir)};
+__attribute__((used)) static Interposer _interpose_readdir MACOS_ATTRIB = {VOIDP_CAST(my_readdir), VOIDP_CAST(readdir)};
 __attribute__((used)) static Interposer _interpose_closedir MACOS_ATTRIB = {VOIDP_CAST(my_closedir), VOIDP_CAST(closedir)};
 __attribute__((used)) static Interposer _interpose_access MACOS_ATTRIB = {VOIDP_CAST(my_access), VOIDP_CAST(access)};
 __attribute__((used)) static Interposer _interpose_fopen MACOS_ATTRIB = {VOIDP_CAST(my_fopen), VOIDP_CAST(fopen)};