chromiumBeta: Fix a compilation error

LLVM 14 doesn't support those build flags yet
(-no-opaque-pointers is the argument for -Xclang):
error: unknown argument: '-no-opaque-pointers'

Those build flags were added in the following commit:
https://source.chromium.org/chromium/chromium/src/+/003067c130958bb2f867324cd675b4e5d1efbf00

pkgs/applications/networking/browsers/chromium/common.nix

@@ -166,6 +166,10 @@ let
       # Workaround/fix for https://bugs.chromium.org/p/chromium/issues/detail?id=1313361:
       substituteInPlace BUILD.gn \
         --replace '"//infra/orchestrator:orchestrator_all",' ""
+      # Disable build flags that require LLVM 15:
+      substituteInPlace build/config/compiler/BUILD.gn \
+        --replace '"-Xclang",' "" \
+        --replace '"-no-opaque-pointers",' ""
     '' + ''
       # remove unused third-party
       for lib in ${toString gnSystemLibraries}; do