Bug 1576515 - Enable PHC on Mac r=glandium

Note that we don't appear to support 32-bit on mac so it'd be redundant to check for it.

Differential Revision: https://phabricator.services.mozilla.com/D124919

build/moz.configure/memory.configure

@@ -77,12 +77,11 @@ def phc_default(milestone, target, replace_malloc_default, replace_malloc):
         return False
     # Both Linux32 and Win32 have frequent crashes when stack tracing (for
     # unclear reasons), so PHC is enabled only on 64-bit only in both cases.
-    #
-    # XXX: PHC is implemented but not yet enabled on Mac. Bug 1576515 is about
-    #      enabling it on Mac, but it is blocked by bug 1035892.
     return (
-        target.os == "GNU" and target.kernel == "Linux" and target.bitness == 64
-    ) or (target.kernel == "WINNT" and target.bitness == 64)
+        (target.os == "GNU" and target.kernel == "Linux" and target.bitness == 64)
+        or (target.kernel == "WINNT" and target.bitness == 64)
+        or (target.os == "OSX")
+    )
 
 
 option(