fix: split clcache into restore/save steps, drop deprecated save-always

actions/cache v5.0.5 marks save-always as deprecated and "not working as
intended". Replace the single cache step with a restore step before the
build and a save step after, guarded by always() so it runs on build
failure too. The save is skipped on an exact cache-hit to avoid redundant
uploads.

https://claude.ai/code/session_01XTvMZtPH8WpuiRBZkqWiHk

Author: claude

.github/workflows/build.yml

@@ -71,15 +71,15 @@ jobs:
           verbose: 1
           create-symlink: true
 
-      - name: Setup cache for clcache
+      - name: Restore cache for clcache
+        id: clcache-restore
         if: ${{ matrix.platform == 'windows-latest' }}
-        uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
+        uses: actions/cache/restore@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
         with:
           path: ${{ github.workspace }}\.clcache
           key: ${{ github.job }}-${{ matrix.platform }}-${{ github.sha }}
           restore-keys: |
             ${{ github.job }}-${{ matrix.platform }}-
-          save-always: true
 
       - name: Create sbom, binary & package
         env:
@@ -94,6 +94,13 @@ jobs:
           python script/build.py
           python script/package.py
 
+      - name: Save cache for clcache
+        if: ${{ always() && matrix.platform == 'windows-latest' && steps.clcache-restore.outputs.cache-hit != 'true' }}
+        uses: actions/cache/save@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
+        with:
+          path: ${{ github.workspace }}\.clcache
+          key: ${{ steps.clcache-restore.outputs.cache-primary-key }}
+
       - name: Store the distribution packages
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
         with: