ci: make fat qt libs thin (#6281)

* ci: strip fat qt binaries

* parallelize

* cache thin qt

* print libs

* change qt install dir in the action

* move qt install logic to separate job

* lookup only

* debug: show contents of QTDIR

* enableCrossOsArchive also when saving

* check one dir up

* change install dir

* keep debugging

* try deleting cache

* force delete cache

* pass gh_token

* pass missing params

* use api

* change cache key, disable cross os archive

* move job directly to steps

* add comments

* set cache param directly

* address comments

* fixup

* Update .ci/thin_macos_qtlib.sh

* resolve qt version

* move resolution to separate script

* use single line for run:

* improve error handling in new scripts

---------

Co-authored-by: ebbit1q <ebbit1q@gmail.com>

.ci/thin_macos_qtlib.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+# The macos binaries from aqt are fat (universal), so we thin them to the target architecture to reduce the size of
+# the packages and caches using lipo.
+
+# This script is meant to be used by the ci enironment on macos runners only.
+# It uses the runner's GITHUB_WORKSPACE env variable.
+arch=$(uname -m)
+nproc=$(sysctl -n hw.ncpu)
+
+function thin() {
+  local libfile=$1
+  if [[ $(file -b --mime-type "$libfile") == application/x-mach-binary* ]]; then
+    echo "Processing $libfile"
+    lipo "$libfile" -thin "$arch" -output "$libfile"
+  fi
+  return 0
+}
+export -f thin  # export to allow use in xargs
+export arch
+set -eo pipefail
+
+echo "::group::Thinning Qt libraries to $arch using $nproc cores"
+find "$GITHUB_WORKSPACE/Qt" -type f -print0 | xargs -0 -n1 -P"$nproc" -I{} bash -c "thin '{}'"
+echo "::endgroup::"