ci: auto-detect the OS instead of relying on NODE_LABELS

And remove WAF_JOBS: waf already defaults to the number of available
CPUs, which is appropriate in most cases, and we can always use the
built-in JOBS variable to override it where necessary.

Change-Id: Id132b9ef8467a563694222ccc64a676cdc076e17

.github/workflows/ci.yml

@@ -27,8 +27,6 @@ jobs:
     runs-on: ${{ matrix.os }}
     env:
       CXX: ${{ matrix.compiler }}
-      NODE_LABELS: Linux Ubuntu
-      WAF_JOBS: 2
     steps:
       - name: Install C++ compiler
         run: |
@@ -52,9 +50,6 @@ jobs:
           - xcode: '13.2'
             os: macos-11
     runs-on: ${{ matrix.os }}
-    env:
-      NODE_LABELS: OSX
-      WAF_JOBS: 3
     steps:
       - name: Set up Xcode
         uses: maxim-lobanov/setup-xcode@v1

.github/workflows/docs.yml

@@ -18,16 +18,11 @@ jobs:
     runs-on: ${{ matrix.os }}
     env:
       JOB_NAME: Docs
-      WAF_JOBS: 3
     steps:
       - name: Checkout
         uses: actions/checkout@v3
       - name: Install dependencies
         run: |
-          case ${RUNNER_OS} in
-            Linux) export NODE_LABELS="Linux Ubuntu" ;;
-            macOS) export NODE_LABELS="OSX" ;;
-          esac
           find .jenkins.d/ -type f -name '[1-9]*.sh' -exec chmod -x '{}' +
           ./.jenkins
       - name: Build documentation