MacPorts vs. Apple compiler issues, Handle

[Riccardo Mottola]

Hi!

I am wondering about differences between Apple clang and MacPorts clang.
I tried to compile ArcticFox on 10.13, but in back compiatibility (10.9 
target on 10.11 SDK got through MacPorts)

Using exactly the same configuration options, MacPort clang 9.0 fails with:

169:29.18 
/Users/multix/code/Arctic-Fox/ipc/testshell/XPCShellEnvironment.cpp:76:13: 
error: reference to 'Handle' is ambiguous
169:29.18 Environment(Handle<JSObject*> global)
169:29.18             ^
169:29.18 
/opt/local/Developer/SDKs/MacOSX10.11.sdk/usr/include/MacTypes.h:249:41: 
note: candidate found by name lookup is 'Handle'
169:29.18 typedef Ptr *                           Handle;
169:29.18                                         ^
169:29.18 
/Users/multix/code/Arctic-Fox/obj-x86_64-apple-darwin17.7.0/dist/include/js/RootingAPI.h:381:25: 
note: candidate found by name lookup is 'JS::Handle'
169:29.18 class MOZ_NONHEAP_CLASS Handle : public js::HandleBase<T>
169:29.18                         ^
169:29.18 1 error generated.


However using apple's clang, all works fine.

MacPort installs:
$ clang-mp-9.0 --version
clang version 9.0.1

Apple:
$ clang --version
Apple LLVM version 9.1.0 (clang-902.0.39.1)

Is there some Apple "trick" or is it the slight compiler difference in 
version?

Thanks,

Riccardo