Add Xcode version selection, with default 11.7, for packaging step.

Author: jonsimantov

.github/workflows/cpp-packaging.yml

@@ -19,11 +19,14 @@ on:
 env:
   # Packaging prerequisites
   # Binutils 2.35.1 released Sep 19, 2020
-  binutilsVer: 2.35.1
+  binutilsVer: "2.35.1"
   # Demumble 1.1.0 released Nov 13, 2018
-  demumbleVer: 1.1.0
+  demumbleVer: "1.1.0"
   # Use SHA256 for hashing files.
-  hashCommand: sha256sum
+  hashCommand: "sha256sum"
+  # Xcode version 11.7 is the version we build the SDK with.
+  # Our MacOS runners will use the version in /Applications/Xcode_${xcodeVersion}.app
+  xcodeVersion: "11.7"
 
 jobs:
   log_inputs:
@@ -64,6 +67,9 @@ jobs:
         - os: macos-latest
           tools_platform: darwin
     steps:
+      - name: setup Xcode version (macos)
+        if: runner.os == "macOS"
+        run: sudo xcode-select -s /Applications/Xcode_${{ env.xcodeVersion }}.app/Contents/Developer
       - name: fetch and build binutils
         run: |
           set +e
@@ -247,6 +253,10 @@ jobs:
           build_type: "Debug"
 
     steps:
+      - name: setup Xcode version (macos)
+        if: runner.os == "macOS"
+        run: sudo xcode-select -s /Applications/Xcode_${{ env.xcodeVersion }}.app/Contents/Developer
+
       - uses: actions/checkout@v2
         with:
           submodules: true
@@ -367,6 +377,10 @@ jobs:
         - sdk_platform: darwin
           runs_on_platform: ubuntu-latest
     steps:
+      - name: setup Xcode version (macos)
+        if: runner.os == "macOS"
+        run: sudo xcode-select -s /Applications/Xcode_${{ env.xcodeVersion }}.app/Contents/Developer
+
       - name: fetch SDK
         uses: actions/[email protected]
         with:
@@ -588,6 +602,10 @@ jobs:
     if: always()
     runs-on: ubuntu-latest
     steps:
+      - name: setup Xcode version (macos)
+        if: runner.os == "macOS"
+        run: sudo xcode-select -s /Applications/Xcode_${{ env.xcodeVersion }}.app/Contents/Developer
+
       - name: download SDK zip
         uses: actions/download-artifact@v2
         with: