Bug 1527371 - Show linker time breakdown for xul.dll r=froydnj

COFF-flavored lld collects timing stats about various phases of linking. This might be useful to have in logs. I left it off in developer builds to avoid spamming tight edit-compile cycles.

Differential Revision: https://phabricator.services.mozilla.com/D33319

--HG--
extra : moz-landing-system : lando

toolkit/library/moz.build

@@ -58,6 +58,10 @@ def Libxul(name, output_category=None):
         # and config/version.mk would lift the $(srcdir)
         RCINCLUDE = '$(DEPTH)/toolkit/library/xulrunner.rc'
 
+    # Show a breakdown of linker time. (Too verbose for local builds.)
+    if CONFIG['CC_TYPE'] == 'clang-cl' and not CONFIG['DEVELOPER_OPTIONS']:
+        LDFLAGS += ['-time']
+
     Libxul_defines()
 
     if CONFIG['MOZ_NEEDS_LIBATOMIC']: