[skip ci] Skip some build checks in PRs (#12608)

* [skip ci] Skip some build checks in PRs

* Remove unused line

* [skip ci] Move parsing to the prepare job, make names more consistent

.github/workflows/build_pull_request.yml

@@ -15,6 +15,8 @@ jobs:
     outputs:
       individualMatrix: ${{ steps.generate-matrices.outputs.individualMatrix }}
       multisrcMatrix: ${{ steps.generate-matrices.outputs.multisrcMatrix }}
+      isIndividualChanged: ${{ steps.parse-changed-files.outputs.isIndividualChanged }}
+      isMultisrcChanged: ${{ steps.parse-changed-files.outputs.isMultisrcChanged }}
     env:
       CI_MODULE_GEN: true
     steps:
@@ -61,9 +63,33 @@ jobs:
             core.setOutput('individualMatrix', { 'chunk': [...Array(numIndividualChunks).keys()] });
             core.setOutput('multisrcMatrix', { 'chunk': [...Array(numMultisrcChunks).keys()] });
 
+      - id: get-changed-files
+        name: Get changed files
+        uses: jitterbit/get-changed-files@v1
+
+      - id: parse-changed-files
+        name: Parse changed files
+        run: |
+          isIndividualChanged=0
+          isMultisrcChanged=0
+          for changedFile in ${{ steps.get-changed-files.outputs.all }}; do
+            if [[ ${changedFile} == src/* ]]; then
+              isIndividualChanged=1
+            elif [[ ${changedFile} == multisrc/* ]]; then
+              isMultisrcChanged=1
+            else
+              isIndividualChanged=1
+              isMultisrcChanged=1
+              break
+            fi
+          done
+          echo "::set-output name=isIndividualChanged::$isIndividualChanged"
+          echo "::set-output name=isMultisrcChanged::$isMultisrcChanged"
+
   build_multisrc:
     name: Build multisrc modules
     needs: prepare
+    if: ${{ needs.prepare.outputs.isMultisrcChanged == '1' }}
     runs-on: ubuntu-latest
     strategy:
       matrix: ${{ fromJSON(needs.prepare.outputs.multisrcMatrix) }}
@@ -97,6 +123,7 @@ jobs:
   build_individual:
     name: Build individual modules
     needs: prepare
+    if: ${{ needs.prepare.outputs.isIndividualChanged == '1' }}
     runs-on: ubuntu-latest
     strategy:
       matrix: ${{ fromJSON(needs.prepare.outputs.individualMatrix) }}