[Sanitizers] Add case MACOS_VERSION_CATALINA

[delcypher]

LGTM

compiler-rt/lib/sanitizer_common/sanitizer_mac.h

enum MacosVersion {
   MACOS_VERSION_MOUNTAIN_LION,
   MACOS_VERSION_MAVERICKS,
   MACOS_VERSION_YOSEMITE,
   MACOS_VERSION_EL_CAPITAN,
   MACOS_VERSION_SIERRA,
   MACOS_VERSION_HIGH_SIERRA,
   MACOS_VERSION_HIGH_SIERRA_DOT_RELEASE_4,
   MACOS_VERSION_MOJAVE,
+  MACOS_VERSION_CATALINA,
   MACOS_VERSION_UNKNOWN_NEWER
 };
 
 MacosVersion GetMacosVersion();
 
 char **GetEnviron();
 
 void RestrictMemoryToMaxAddress(uptr max_address);

compiler-rt/lib/sanitizer_common/sanitizer_mac.cc

switch (major) {
     case 14: return MACOS_VERSION_YOSEMITE;
     case 15: return MACOS_VERSION_EL_CAPITAN;
     case 16: return MACOS_VERSION_SIERRA;
     case 17:
       // Not a typo, 17.5 Darwin Kernel Version maps to High Sierra 10.13.4.
       if (minor >= 5)
         return MACOS_VERSION_HIGH_SIERRA_DOT_RELEASE_4;
       return MACOS_VERSION_HIGH_SIERRA;
-    case 18:
-      return MACOS_VERSION_MOJAVE;
+    case 18: return MACOS_VERSION_MOJAVE;
+    case 19: return MACOS_VERSION_CATALINA;
     default:
       if (major < 9) return MACOS_VERSION_UNKNOWN;
       return MACOS_VERSION_UNKNOWN_NEWER;
   }
 }
 
 MacosVersion GetMacosVersion() {
   atomic_uint32_t *cache =