workflows: Use macos-11 runners

macos-10.15 is deprecated and will be removed.

(cherry picked from commit d9e02a3)

Author: tstellar

.github/workflows/llvm-project-tests.yml

@@ -39,9 +39,7 @@ jobs:
           - windows-2019
           # We're using a specific version of macOS due to:
           # https://github.com/actions/virtual-environments/issues/5900
-          # We need addtional testing to see if our workaround works for
-          # new macOS builds.
-          - macOS-10.15
+          - macOS-11
     steps:
       - name: Setup Windows
         if: startsWith(matrix.os, 'windows')
@@ -74,7 +72,7 @@ jobs:
         env:
           # Workaround for https://github.com/actions/virtual-environments/issues/5900.
           # This should be a no-op for non-mac OSes
-          PKG_CONFIG_PATH: /usr/local/Homebrew/Library/Homebrew/os/mac/pkgconfig//11
+          PKG_CONFIG_PATH: /usr/local/Homebrew/Library/Homebrew/os/mac/pkgconfig//12
         with:
           cmake_args: '-GNinja -DLLVM_ENABLE_PROJECTS="${{ inputs.projects }}" -DCMAKE_BUILD_TYPE=Release -DLLDB_INCLUDE_TESTS=OFF -DCMAKE_C_COMPILER_LAUNCHER=sccache -DCMAKE_CXX_COMPILER_LAUNCHER=sccache'
           build_target:  '${{ inputs.build_target }}'