add pfunit cache

.github/workflows/extbuild.yml

@@ -21,6 +21,7 @@ jobs:
       # Versions of all dependencies can be updated here - these match tag names in the github repo
       ESMF_VERSION: v8.6.1
       ParallelIO_VERSION: pio2_6_2
+      PFUNIT_VERSION: v4.9.0
     steps:
       - id: checkout-share
         uses: actions/checkout@v4
@@ -80,13 +81,20 @@ jobs:
         uses: actions/checkout@v4
         with:
           path: pfunit
+          ref: ${PFUNIT_VERSION}
           repository: Goddard-Fortran-Ecosystem/pFUnit
       - name: build PFUNIT
         run: |
           pushd pfunit
-          cmake -B build
-          cmake --build build -DSKIP_MPI=YES -DSKIP_OPENMP=YES
+          cmake -DSKIP_MPI=YES -DSKIP_OPENMP=YES -B build
+          cmake --build build 
           popd
+      - name: Cache PFUNIT
+        id: cache-pfunit
+        uses: actions/cache@v4
+        with:
+          path: pfunit
+          key: ${{ runner.os }}-${{ env.PFUNIT_VERSION }}
 #     the following can be used by developers to login to the github server in case of errors
 #     see https://github.com/marketplace/actions/debugging-with-tmate for further details
 #      - name: Setup tmate session