Guard sccache launcher exports in android release build-aar

Co-authored-by: kirklandsign <107070759+kirklandsign@users.noreply.github.com>
Agent-Logs-Url: https://github.com/pytorch/executorch/sessions/d70da9ba-dce7-40f4-9e9d-32f6e0d20cde

Author: Copilot

.github/workflows/android-release-artifacts.yml

@@ -92,9 +92,11 @@ jobs:
         run: |
           set -eux
 
-          # Use sccache for NDK compiler as well
-          export CMAKE_CXX_COMPILER_LAUNCHER=sccache
-          export CMAKE_C_COMPILER_LAUNCHER=sccache
+          # Use sccache for NDK/compiler builds when available.
+          if command -v sccache >/dev/null 2>&1; then
+            export CMAKE_CXX_COMPILER_LAUNCHER=sccache
+            export CMAKE_C_COMPILER_LAUNCHER=sccache
+          fi
 
           # The generic Linux job chooses to use base env, not the one setup by the image
           eval "$(conda shell.bash hook)"