Bug 1652374 - Use LLD for non-PGO-profile-use clang builds on automation. r=froydnj

Differential Revision: https://phabricator.services.mozilla.com/D85536

build/unix/mozconfig.linux

@@ -12,3 +12,9 @@ base-toolchains*)
 esac
 
 export MOZ_NO_PIE_COMPAT=1
+
+if [ -z "$USE_ARTIFACT" -a -z "$TASKCLUSTER_PGO_PROFILE_USE" -a -z "$FORCE_GCC" ]; then
+    # Use LLD on most builds, for faster builds, but not on shippable ones because we
+    # want to keep elfhack there, which is incompatible.
+    ac_add_options --enable-linker=lld
+fi