ci: move to macOS 11 and 20.04 (#651)

Signed-off-by: Christoph Settgast <csett86@web.de>

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ on:
 jobs:
   build-linux:
     name: Linux
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@v2
     - uses: actions/setup-node@v1
@@ -31,17 +31,12 @@ jobs:
         npm run dist
   build-mac:
     name: macOS
-    runs-on: macos-10.15
+    runs-on: macos-11
     steps:
     - uses: actions/checkout@v2
     - uses: actions/setup-node@v1
       with:
         node-version: '14.x'
-    - name: Fixup Xcode
-      # https://github.com/actions/virtual-environments/issues/2557
-      run: |
-        sudo xcode-select -s "/Applications/Xcode_12.4.app"
-        sudo rm -Rf /Library/Developer/CommandLineTools/SDKs/*
     - name: Build it
       env:
         GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}