diff --git a/.github/workflows/runnable_cxx.yml b/.github/workflows/runnable_cxx.yml
index caee3f0b6e..fa053cc4a1 100644
--- a/.github/workflows/runnable_cxx.yml
+++ b/.github/workflows/runnable_cxx.yml
@@ -56,9 +56,9 @@ jobs:
       # very few PRs actually benefit from this.
       fail-fast: false
       matrix:
-        # OSX 10.15, Ubuntu 18.04 in order to support older LLVM / GCC
+        # Mac OS 11, Ubuntu 18.04 in order to support older LLVM / GCC
         # Ubuntu 20.04 in order to support newer LLVM / GCC
-        os: [ macOS-10.15, ubuntu-18.04, ubuntu-20.04, windows-2019 ]
+        os: [ macOS-11, ubuntu-18.04, ubuntu-20.04, windows-2019 ]
 
         target: [
           # Versions of clang earlier than 8 are not available on 18.04
@@ -99,17 +99,17 @@ jobs:
           - { os: ubuntu-20.04, target: g++-6 }
           - { os: ubuntu-20.04, target: g++-5 }
           # OSX only supports clang
-          - { os: macOS-10.15, target: g++-11 }
-          - { os: macOS-10.15, target: g++-10 }
-          - { os: macOS-10.15, target: g++-9 }
-          - { os: macOS-10.15, target: g++-8 }
-          - { os: macOS-10.15, target: g++-7 }
-          - { os: macOS-10.15, target: g++-6 }
-          - { os: macOS-10.15, target: g++-5 }
-          - { os: macOS-10.15, target: msvc-2019 }
-          - { os: macOS-10.15, target: msvc-2017 }
-          - { os: macOS-10.15, target: msvc-2015 }
-          - { os: macOS-10.15, target: msvc-2013 }
+          - { os: macOS-11, target: g++-11 }
+          - { os: macOS-11, target: g++-10 }
+          - { os: macOS-11, target: g++-9 }
+          - { os: macOS-11, target: g++-8 }
+          - { os: macOS-11, target: g++-7 }
+          - { os: macOS-11, target: g++-6 }
+          - { os: macOS-11, target: g++-5 }
+          - { os: macOS-11, target: msvc-2019 }
+          - { os: macOS-11, target: msvc-2017 }
+          - { os: macOS-11, target: msvc-2015 }
+          - { os: macOS-11, target: msvc-2013 }
           # We don't test g++ on Windows as DMD only mangles for MSVC
           - { os: windows-2019, target: g++-11 }
           - { os: windows-2019, target: g++-10 }
@@ -157,13 +157,13 @@ jobs:
           # Platform boilerplate
           - { os: ubuntu-18.04, arch: x86_64-linux-gnu-ubuntu-18.04 }
           - { os: ubuntu-20.04, arch: x86_64-linux-gnu-ubuntu-20.04 }
-          - { os: macOS-10.15,  arch: x86_64-apple-darwin }
+          - { os: macOS-11,  arch: x86_64-apple-darwin }
           # Clang 9.0.0 have a different arch for OSX
-          - { os: macOS-10.15, target: clang-9.0.0, arch: x86_64-darwin-apple }
+          - { os: macOS-11, target: clang-9.0.0, arch: x86_64-darwin-apple }
           # Those targets will generate artifacts that can be used by other testers
           - { storeArtifacts: false }
           - { os: ubuntu-18.04, target: g++-9,       storeArtifacts: true }
-          - { os: macOS-10.15,  target: clang-9.0.0, storeArtifacts: true }
+          - { os: macOS-11,  target: clang-9.0.0, storeArtifacts: true }
           #- { os: windows-2019, target: msvc-2019,   storeArtifacts: true }
 
     # We're using the latest available images at the time of this commit.
@@ -221,7 +221,7 @@ jobs:
       uses: actions/cache@v1
       with:
         path: ${{ github.workspace }}/clang+llvm-${{ matrix.cxx-version }}-${{ matrix.arch }}/
-        key: ${{ matrix.cxx-version }}-${{ matrix.arch }}-1
+        key: ${{ matrix.cxx-version }}-${{ matrix.arch }}-2022-09-25-2121
 
     - name: '[Posix] Setting up clang ${{ matrix.cxx-version }}'
       if: matrix.compiler == 'clang' && runner.os != 'Windows' && steps.cache-clang.outputs.cache-hit != 'true'
@@ -236,7 +236,7 @@ jobs:
         # On OSX, the system header are installed via `xcode-select` and not distributed with clang
         # Since some part of the testsuite rely on CC being only a binary (not a command),
         # and config files where only introduced from 6.0.0, use a wrapper script.
-        if [ "${{ matrix.os }}" == "macOS-10.15" ]; then
+        if [ "${{ matrix.os }}" == "macOS-11" ]; then
           # Note: heredoc shouldn't be indented
           cat << 'EOF' > ${TMP_CC}-wrapper
         #!/bin/bash
@@ -258,9 +258,10 @@ jobs:
       if: matrix.compiler == 'clang' && runner.os != 'Windows'
       run: |
         TMP_CC='${{ github.workspace }}/clang+llvm-${{ matrix.cxx-version }}-${{ matrix.arch }}/bin/clang'
-        if [ "${{ matrix.os }}" == "macOS-10.15" ]; then
+        if [ "${{ matrix.os }}" == "macOS-11" ]; then
           echo "CC=${TMP_CC}-wrapper" >> $GITHUB_ENV
           echo "CXX=${TMP_CC}++-wrapper" >> $GITHUB_ENV
+          echo "SDKROOT=$(xcrun --show-sdk-path)" >> $GITHUB_ENV
         else
           echo "CC=${TMP_CC}" >> $GITHUB_ENV
           echo "CXX=${TMP_CC}++" >> $GITHUB_ENV