Bug 1900780 follow-up: Fix builds without the crash reporter. rs=bustage-fix

--HG--
extra : rebase_source : a43300245592d01c4e04c47b3560cf8c1f21749e
extra : amend_source : cc4266c05f7653aa6b539f69dcea6eabc25d5e3a

rust/gkrust/moz.build

@@ -6,7 +6,8 @@
 
 include("/toolkit/library/rust/moz.build")
 
-RUST_TEST_FEATURES.remove("gkrust-shared/crashreporter")
+if CONFIG["MOZ_CRASHREPORTER"]:
+    RUST_TEST_FEATURES.remove("gkrust-shared/crashreporter")
 RUST_TEST_FEATURES.remove("crashreporter/mock")
 
 # Defined in /toolkit/library/rust/moz.build