chore(ci): scope build cache to Package.resolved hash (#4195)

The workflow build cache key was `Amplify-<platform>-<xcode-version>-build-cache`,
which is stable per platform+Xcode forever. When `aws-sdk-swift` (or any SPM
dependency) is bumped, `Package.resolved` changes and newly-generated source
references symbols in modules like `SmithyXML` that do not exist in the cached
`AWSClientRuntime.framework` from a prior commit. The result is linker errors
such as:

    Undefined symbol: static SmithyXML.Reader.from(data: Foundation.Data) -> Reader
    Undefined symbol: type metadata accessor for SmithyXML.Reader
    Ld .../AWSClientRuntime.framework/AWSClientRuntime

The SPM dependencies cache already includes `hashFiles('Package.resolved')` in
its key, so it self-invalidates correctly. Apply the same pattern to the build
cache key so a `Package.resolved` change moves to a fresh cache bucket, and
stale buckets expire naturally under GitHub's cache LRU.

Updates every workflow that reads or writes the build cache:
- build_scheme.yml
- run_integration_tests.yml
- run_unit_tests.yml
- integ_test_auth_webauthn.yml
- integ_test_push_notifications.yml

The save step in build_scheme.yml uses `steps.build-cache.outputs.cache-primary-key`,
so it automatically writes to the new hashed bucket. The existing "Delete the old
build cache" step continues to remove only the matching bucket before overwriting.

Author: harsh62

.github/workflows/build_scheme.yml

@@ -68,7 +68,7 @@ jobs:
         uses: actions/cache/restore@1bd1e32a3bdc45362d1e726936510720a7c30a57 # v4.2.0
         with:
           path: ${{ github.workspace }}/Build
-          key: Amplify-${{ inputs.platform }}-${{ steps.platform.outputs.xcode-version }}-build-cache
+          key: Amplify-${{ inputs.platform }}-${{ steps.platform.outputs.xcode-version }}-build-cache-${{ hashFiles('Package.resolved') }}
 
       - name: Build ${{ inputs.scheme }}
         id: build-package

.github/workflows/integ_test_auth_webauthn.yml

@@ -73,7 +73,7 @@ jobs:
         uses: actions/cache/restore@1bd1e32a3bdc45362d1e726936510720a7c30a57 # v4.2.0
         with:
           path: ${{ github.workspace }}/Build
-          key: Amplify-iOS-${{ steps.platform.outputs.xcode-version }}-build-cache
+          key: Amplify-iOS-${{ steps.platform.outputs.xcode-version }}-build-cache-${{ hashFiles('Package.resolved') }}
 
       - name: Run Local Server
         run: |

.github/workflows/integ_test_push_notifications.yml

@@ -91,7 +91,7 @@ jobs:
         uses: actions/cache/restore@1bd1e32a3bdc45362d1e726936510720a7c30a57 # v4.2.0
         with:
           path: ${{ github.workspace }}/Build
-          key: Amplify-${{ matrix.platform }}-${{ steps.platform.outputs.xcode-version }}-build-cache
+          key: Amplify-${{ matrix.platform }}-${{ steps.platform.outputs.xcode-version }}-build-cache-${{ hashFiles('Package.resolved') }}
 
       - name: Run Local Server
         run: |

.github/workflows/run_integration_tests.yml

@@ -94,7 +94,7 @@ jobs:
         uses: actions/cache/restore@1bd1e32a3bdc45362d1e726936510720a7c30a57 # v4.2.0
         with:
           path: ${{ github.workspace }}/Build
-          key: Amplify-${{ inputs.platform }}-${{ steps.platform.outputs.xcode-version }}-build-cache
+          key: Amplify-${{ inputs.platform }}-${{ steps.platform.outputs.xcode-version }}-build-cache-${{ hashFiles('Package.resolved') }}
 
       - name: Run ${{ inputs.platform }} Integration Tests
         id: run-tests

.github/workflows/run_unit_tests.yml

@@ -86,7 +86,7 @@ jobs:
         uses: actions/cache/restore@1bd1e32a3bdc45362d1e726936510720a7c30a57 # v4.2.0
         with:
           path: ${{ github.workspace }}/Build
-          key: Amplify-${{ inputs.platform }}-${{ steps.platform.outputs.xcode-version }}-build-cache
+          key: Amplify-${{ inputs.platform }}-${{ steps.platform.outputs.xcode-version }}-build-cache-${{ hashFiles('Package.resolved') }}
 
       - name: Run ${{ inputs.platform }} Unit Tests
         id: run-tests