Added LLVM 15 CI

Signed-off-by: Nick Avramoussis <4256455+Idclip@users.noreply.github.com>

Author: Idclip

.github/workflows/weekly.yml

@@ -233,8 +233,7 @@ jobs:
       matrix:
         config:
           - { cxx: 'clang++', build: 'Release', llvm: '14', dir: '@14' }
-          # Can't support LLVM >= 15
-          #- { cxx: 'clang++', build: 'Release', llvm: 'latest', dir: '' }
+          - { cxx: 'clang++', build: 'Release', llvm: 'latest', dir: '' }
       fail-fast: false
     steps:
       - uses: actions/checkout@v2