CI: Set ccache directory explicitly

ccache uses various rules to determine the cache directory, which may
result in different CI containers having different paths.

.github/workflows/cts_ci.yml

@@ -150,17 +150,21 @@ jobs:
  # Use ccache's "depend mode" to work around DPC++ issue (see https://github.com/intel/llvm/issues/5260)
  # This requires compilation with -MD, which is enabled because we use the Ninja generator
  # Using this mode should not have any practical disadvantages
+ - name: Set ccache environment variables
+ run: |
+ echo "CCACHE_DEPEND=1" >> "$GITHUB_ENV"
+ echo "CCACHE_DIR=~/.ccache" >> "$GITHUB_ENV"
  - name: Build 'oclmath'
  working-directory: ${{ env.container-workspace }}/build
- run: CCACHE_DEPEND=1 cmake --build . --target oclmath
+ run: cmake --build . --target oclmath
  - name: Build 'util'
  working-directory: ${{ env.container-workspace }}/build
- run: CCACHE_DEPEND=1 cmake --build . --target util
+ run: cmake --build . --target util
  - name: Build all supported test categories
  working-directory: ${{ env.container-workspace }}/build
  run: |
  TS_BEFORE=$(date +%s)
- CCACHE_DEPEND=1 cmake --build . --target test_all --parallel ${{ env.parallel-build-jobs }}
+ cmake --build . --target test_all --parallel ${{ env.parallel-build-jobs }}
  TS_AFTER=$(date +%s)
  ELAPSED=$(($TS_AFTER - $TS_BEFORE))
  sort --numeric-sort --reverse --output=build_times.log build_times.log