try CI build using custom libcxx

Author: JoshuaBehrens

.github/workflows/build-test.yml

@@ -52,9 +52,9 @@ jobs:
                 if: ${{ matrix.operating-system == 'ubuntu-latest' }}
                 run: |
                     sudo apt update
-                    sudo apt install -y clang-19 lld-19
-                    sudo update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-19 100
-                    sudo update-alternatives --install /usr/bin/clang clang /usr/bin/clang-19 100
+                    sudo apt install -y clang-20 lld-20
+                    sudo update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-20 100
+                    sudo update-alternatives --install /usr/bin/clang clang /usr/bin/clang-20 100
                 
             -   name: Build v8 ${{ matrix.v8-versions }}
                 if: steps.v8-build-cache.outputs.cache-hit != 'true'
@@ -80,7 +80,7 @@ jobs:
 
                     # Setup GN
                     # Warnings are no errors - @see https://issues.chromium.org/issues/42203398#comment9
-                    tools/dev/v8gen.py -vv $V8CONFIG -- is_component_build=true use_custom_libcxx=false treat_warnings_as_errors=false
+                    tools/dev/v8gen.py -vv $V8CONFIG -- is_component_build=true use_custom_libcxx=true treat_warnings_as_errors=false
 
                     # Build
                     ninja -C out.gn/$V8CONFIG/
@@ -139,9 +139,9 @@ jobs:
                 if: ${{ matrix.operating-system == 'ubuntu-latest' }}
                 run: |
                     sudo apt update
-                    sudo apt install -y clang-19 lld-19
-                    sudo update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-19 100
-                    sudo update-alternatives --install /usr/bin/clang clang /usr/bin/clang-19 100
+                    sudo apt install -y clang-20 lld-20
+                    sudo update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-20 100
+                    sudo update-alternatives --install /usr/bin/clang clang /usr/bin/clang-20 100
 
             -   name: Download cache v8 ${{ matrix.v8-versions }} build
                 uses: actions/cache/restore@v4