Bug 1960869 - Fix builds with --project=memory r=glandium

* set FINAL_LIBRARY in mfbt and third_party_fmt only when not using
   --enable-project=memory
 * include third_party/fmt in memory/app.mozbuild

Differential Revision: https://phabricator.services.mozilla.com/D245716

memory/app.mozbuild

@@ -13,6 +13,7 @@ EXPORTS.mozilla += [
 DIRS += [
     "/memory",
     "/mfbt",
+    "/third_party/fmt",
 ]
 
 EXPORTS.mozilla += [

mfbt/moz.build

@@ -199,4 +199,5 @@ DEFINES["MOZ_SUPPORT_LEAKCHECKING"] = True
 # don't use mfbt.
 DIRS += ["../build/pure_virtual"]
 
-FINAL_LIBRARY = "mozglue"
+if CONFIG["MOZ_BUILD_APP"] != "memory":
+    FINAL_LIBRARY = "mozglue"

third_party/fmt/moz.build

@@ -4,7 +4,8 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-FINAL_LIBRARY = "mozglue"
+if CONFIG["MOZ_BUILD_APP"] != "memory":
+  FINAL_LIBRARY = "mozglue"
 
 with Files('**'):
     BUG_COMPONENT = ('Core', 'mozglue')