Bug 1720448 - Build wasi-sysroot on bigger worker types. r=firefox-build-system-reviewers,mhentges

A large part of those builds actually build clang, which can benefit
from a larger number of cores.

Differential Revision: https://phabricator.services.mozilla.com/D119872

taskcluster/ci/toolchain/misc.yml

@@ -153,6 +153,7 @@ wasi-sysroot-11:
         local-toolchain: true
     treeherder:
         symbol: TL(wasi-sysroot-11)
+    worker-type: b-linux-xlarge
     run-on-projects: [trunk]
     run:
         script: build-wasi-sysroot.sh
@@ -172,6 +173,7 @@ wasi-sysroot-12:
         local-toolchain: true
     treeherder:
         symbol: TL(wasi-sysroot-12)
+    worker-type: b-linux-xlarge
     run-on-projects: [trunk]
     run:
         script: build-wasi-sysroot.sh