misc,tests: Improve daily cache handling.

.github/workflows/daily-tests.yaml

@@ -43,21 +43,17 @@ jobs:
               run: rm -rf ./* || true rm -rf ./.??* || true rm -rf ~/.cache || true
             - uses: actions/checkout@v4
 
-            - name: Cache build/NULL
-              uses: actions/cache@v4
+            - name: Restore build/NULL cache
+              uses: actions/restore@v4
               with:
                   path: build/NULL
                   key: testlib-build-null-${{ hashFiles('src/**') }}
-                  restore-keys: |
-                      testlib-build-null
 
-            - name: Cache build/ALL
-              uses: actions/cache@v4
+            - name: Restore build/ALL cache
+              uses: actions/restore@v4
               with:
                   path: build/ALL
                   key: testlib-build-all-${{ hashFiles('src/**') }}
-                  restore-keys: |
-                      testlib-build-all
 
             - name: long ${{ matrix.test-type }} tests
               working-directory: ${{ github.workspace }}/tests
@@ -71,6 +67,21 @@ jobs:
                   name: ${{ env.MY_STEP_VAR }}
                   path: tests/testing-results
                   retention-days: 7
+
+            - name: Save build/NULL cache
+              uses: actions/save-cache@v2
+              if: ${{ hashFiles('build/NULL/') != '' }}
+              with:
+                  path: build/NULL
+                  key: testlib-build-null-${{ hashFiles('src/**') }}
+
+            - name: Save build/ALL cache
+              uses: actions/save-cache@v2
+              if: ${{ hashFiles('build/ALL/') != '' }}
+              with:
+                  path: build/ALL
+                  key: testlib-build-all-${{ hashFiles('src/**') }}
+
             - run: echo "This job's status is ${{ job.status }}."
 
   # split library example tests into runs based on Suite UID