Bug 1630041 - Allow setting the update host via set define at build time. r=glandium

Bug 1568994 moved the URL for the update server to application.ini. Thunderbird
uses a different hostname for the update URL; the URL path is the same.

I've added a set_config('MOZ_APPUPDATE_HOST') to Thunderbird's moz.configure
file which will override the default.

Differential Revision: https://phabricator.services.mozilla.com/D70964

build/application.ini.in

@@ -52,5 +52,5 @@ ServerURL=https://crash-reports.mozilla.com/submit?id=@MOZ_APP_ID@&version=@MOZ_
 
 #if MOZ_UPDATER
 [AppUpdate]
-URL=https://aus5.mozilla.org/update/6/%PRODUCT%/%VERSION%/%BUILD_ID%/%BUILD_TARGET%/%LOCALE%/%CHANNEL%/%OS_VERSION%/%SYSTEM_CAPABILITIES%/%DISTRIBUTION%/%DISTRIBUTION_VERSION%/update.xml
+URL=https://@MOZ_APPUPDATE_HOST@/update/6/%PRODUCT%/%VERSION%/%BUILD_ID%/%BUILD_TARGET%/%LOCALE%/%CHANNEL%/%OS_VERSION%/%SYSTEM_CAPABILITIES%/%DISTRIBUTION%/%DISTRIBUTION_VERSION%/update.xml
 #endif

build/moz.build

@@ -76,6 +76,10 @@ if CONFIG['MOZ_APP_BASENAME']:
         if CONFIG[var]:
             appini_defines[var] = True
 
+    appini_defines['MOZ_APPUPDATE_HOST'] = 'aus5.mozilla.org'
+    if CONFIG['MOZ_APPUPDATE_HOST']:
+        appini_defines['MOZ_APPUPDATE_HOST'] = CONFIG['MOZ_APPUPDATE_HOST']
+
     GeneratedFile(
         'application.ini',
         script='../python/mozbuild/mozbuild/action/preprocessor.py',
@@ -83,7 +87,7 @@ if CONFIG['MOZ_APP_BASENAME']:
         inputs=['application.ini.in'],
         flags=['-D%s=%s' % (k, '1' if v is True else v)
                for k, v in sorted(appini_defines.items(), key=lambda t: t[0])])
-    
+
     FINAL_TARGET_FILES += ['!application.ini']
     if CONFIG['MOZ_WIDGET_TOOLKIT'] != 'android' and CONFIG['MOZ_UPDATER']:
         FINAL_TARGET_PP_FILES += ['update-settings.ini']