8310259: Pin msys2/setup-msys2 github action to a specific commit

Reviewed-by: mbaesken
Backport-of: 959a61fdd483c9523764b9ba0972f59ca06db0ee

Author: GoeLin

.github/actions/get-msys2/action.yml

@@ -30,7 +30,8 @@ runs:
   using: composite
   steps:
     - name: 'Install MSYS2'
-      uses: msys2/setup-msys2@v2
+      # use a specific release of msys2/setup-msys2 to prevent jtreg build failures on newer release
+      uses: msys2/setup-msys2@7efe20baefed56359985e327d329042cde2434ff
       with:
         install: 'autoconf tar unzip zip make'
         path-type: minimal