Bug 1847156 - Use a one-off extra_mozconfig_content for linux64-aarch64 builds. r=firefox-build-system-reviewers,taskgraph-reviewers,releng-reviewers,gbrown,ahochheiden,jcristau

The only differences between the linux64-aarch64 mozconfigs and linux64
mozconfigs are:
 - unset NASM
 - ac_add_options --target=aarch64
 - unset MOZ_STDCXX_COMPAT

The mozconfig is only used once, so we can use a one-off config
instead.

While here, we remove `unset NASM`, which has been useless since bug
1686646.

Differential Revision: https://phabricator.services.mozilla.com/D185389

browser/config/mozconfigs/linux64-aarch64/common-opt

@@ -1,19 +0,0 @@
-# This file is sourced by the nightly, beta, and release mozconfigs.
-
-ac_add_options --enable-update-channel=${MOZ_UPDATE_CHANNEL}
-ac_add_options --with-google-location-service-api-keyfile=/builds/gls-gapi.data
-ac_add_options --with-google-safebrowsing-api-keyfile=/builds/sb-gapi.data
-ac_add_options --with-mozilla-api-keyfile=/builds/mozilla-desktop-geoloc-api.key
-
-. $topsrcdir/build/unix/mozconfig.linux
-
-unset NASM
-ac_add_options --target=aarch64
-
-# Needed to enable breakpad in application.ini
-export MOZILLA_OFFICIAL=1
-
-# Package js shell.
-export MOZ_PACKAGE_JSSHELL=1
-
-unset MOZ_STDCXX_COMPAT

browser/config/mozconfigs/linux64-aarch64/opt

@@ -1,5 +0,0 @@
-. "$topsrcdir/browser/config/mozconfigs/linux64-aarch64/common-opt"
-
-ac_add_options --with-branding=browser/branding/nightly
-
-. "$topsrcdir/build/mozconfig.common.override"

taskcluster/ci/build/linux.yml

@@ -1730,10 +1730,11 @@ linux64-aarch64/opt:
             - builds/releng_base_firefox.py
             - builds/releng_base_linux_64_builds.py
         extra-config:
-            mozconfig_platform: linux64-aarch64
+            extra_mozconfig_content:
+                - ac_add_options --target=aarch64
+                - unset MOZ_STDCXX_COMPAT
         script: "mozharness/scripts/fx_desktop_build.py"
         secrets: true
-        mozconfig-variant: opt
         tooltool-downloads: public
     run-on-projects: ['integration']
     fetches: