Bug 1691719 - Don't explicitly activate supplemental fonts directory when building with pre-Catalina SDK, as the fonts are automatically made available. r=lsalzman

Differential Revision: https://phabricator.services.mozilla.com/D105042

gfx/thebes/gfxMacPlatformFontList.mm

@@ -814,9 +814,14 @@ void gfxSingleFaceMacFontFamily::ReadOtherFamilyNames(gfxPlatformFontList* aPlat
 // under /System/Fonts. Whether they're exposed in the font list by default
 // depends on the SDK used; when built with SDK 10.15, they're absent. So
 // we explicitly activate them to be sure they'll be available.
+#if __MAC_OS_X_VERSION_MAX_ALLOWED < 101500
+static const nsLiteralCString kLangFontsDirs[] = {
+    "/Library/Application Support/Apple/Fonts/Language Support"_ns};
+#else
 static const nsLiteralCString kLangFontsDirs[] = {
     "/Library/Application Support/Apple/Fonts/Language Support"_ns,
     "/System/Library/Fonts/Supplemental"_ns};
+#endif
 
 gfxMacPlatformFontList::gfxMacPlatformFontList()
     : gfxPlatformFontList(false), mDefaultFont(nullptr), mUseSizeSensitiveSystemFont(false) {