ci(cache): revert YAML anchors in composite actions — GHA rejects them

Run 24745149414 failed at action-load time with:

    /home/runner/.../.github/actions/build-llvm/action.yml:
      Anchors are not currently supported. Remove the anchor
      'ccache-llvm-env'

GHA's composite-action manifest loader (ActionManifestManagerLegacy)
explicitly rejects YAML anchors, independent of whether the underlying
YAML library supports them (PyYAML parses these fine; the workflow
parser apparently also does — only action.yml is restricted).

Restore the explicit duplicated CCACHE_* env blocks on the Build and
Show-ccache-stats steps in build-llvm/action.yml and build-solc/action.yml,
with a comment noting why we can't dedupe.

Author: nebasuke

.github/actions/build-llvm/action.yml

@@ -120,13 +120,14 @@ runs:
     # sccache is broken with cmake+ninja+clang on MSYS2/Windows
     # (https://github.com/mozilla/sccache/issues/1097). Using ccache everywhere.
     #
-    # The &ccache-llvm-env anchor keeps this block in sync with the Build LLVM
-    # and Show ccache stats steps — composite-action sibling steps don't share
-    # env, so we'd otherwise duplicate four variables three times.
+    # The four CCACHE_* env vars below are duplicated on the Build LLVM and
+    # Show ccache stats steps. YAML anchors/merge-keys would dedupe but GHA's
+    # composite-action manifest loader rejects anchors — keep them in sync by
+    # hand.
     - name: Set up compiler cache
       if: steps.llvm-artifact-cache.outputs.cache-hit != 'true'
       uses: hendrikmuhs/ccache-action@a1209f81afb8c005c13b4296c32e363431bffea5 # v1.2.14
-      env: &ccache-llvm-env
+      env:
         CCACHE_DIR: ${{ runner.temp }}/ccache-llvm
         CCACHE_BASEDIR: ${{ github.workspace }}
         CCACHE_NOHASHDIR: "true"
@@ -144,7 +145,10 @@ runs:
       shell: ${{ runner.os == 'Windows' && 'msys2 {0}' || 'bash' }}
       working-directory: ${{ inputs.working-dir }}
       env:
-        <<: *ccache-llvm-env
+        CCACHE_DIR: ${{ runner.temp }}/ccache-llvm
+        CCACHE_BASEDIR: ${{ github.workspace }}
+        CCACHE_NOHASHDIR: "true"
+        CCACHE_COMPILERCHECK: "content"
         VERBOSE: 1
         LIBSTDCPP_SOURCE_PATH: "${{ runner.temp }}/msys64/mingw64/lib/libstdc++.a"
       run: |
@@ -171,7 +175,11 @@ runs:
       if: always() && steps.llvm-artifact-cache.outputs.cache-hit != 'true'
       continue-on-error: true
       shell: ${{ runner.os == 'Windows' && 'msys2 {0}' || 'bash' }}
-      env: *ccache-llvm-env
+      env:
+        CCACHE_DIR: ${{ runner.temp }}/ccache-llvm
+        CCACHE_BASEDIR: ${{ github.workspace }}
+        CCACHE_NOHASHDIR: "true"
+        CCACHE_COMPILERCHECK: "content"
       run: ccache --show-stats
 
     - name: Save LLVM artifact cache

.github/actions/build-solc/action.yml

@@ -67,13 +67,14 @@ runs:
     # matches the LLVM pattern and blocks future prefix-collision if more
     # dimensions are added.
     #
-    # The &ccache-solc-env anchor keeps this block in sync with the Build solc
-    # and Show ccache stats steps — composite-action sibling steps don't share
-    # env, so we'd otherwise duplicate four variables three times.
+    # The four CCACHE_* env vars below are duplicated on the Build solc and
+    # Show ccache stats steps. YAML anchors/merge-keys would dedupe but GHA's
+    # composite-action manifest loader rejects anchors — keep them in sync by
+    # hand.
     - name: Set up compiler cache for solc
       if: steps.solc-artifact-cache.outputs.cache-hit != 'true'
       uses: hendrikmuhs/ccache-action@a1209f81afb8c005c13b4296c32e363431bffea5 # v1.2.14
-      env: &ccache-solc-env
+      env:
         CCACHE_DIR: ${{ runner.temp }}/ccache-solc
         CCACHE_BASEDIR: ${{ github.workspace }}
         CCACHE_NOHASHDIR: "true"
@@ -92,7 +93,10 @@ runs:
       working-directory: ${{ inputs.working-dir }}/..
       shell: ${{ runner.os == 'Windows' && 'msys2 {0}' || 'bash' }}
       env:
-        <<: *ccache-solc-env
+        CCACHE_DIR: ${{ runner.temp }}/ccache-solc
+        CCACHE_BASEDIR: ${{ github.workspace }}
+        CCACHE_NOHASHDIR: "true"
+        CCACHE_COMPILERCHECK: "content"
         CXXFLAGS: "-Wno-narrowing"
       run: |
         set -x
@@ -108,7 +112,11 @@ runs:
       if: always() && steps.solc-artifact-cache.outputs.cache-hit != 'true'
       continue-on-error: true
       shell: ${{ runner.os == 'Windows' && 'msys2 {0}' || 'bash' }}
-      env: *ccache-solc-env
+      env:
+        CCACHE_DIR: ${{ runner.temp }}/ccache-solc
+        CCACHE_BASEDIR: ${{ github.workspace }}
+        CCACHE_NOHASHDIR: "true"
+        CCACHE_COMPILERCHECK: "content"
       run: ccache --show-stats
 
     - name: Save solc artifact cache