[libc] add uefi fullbuild to workflows

Author: RossComputerGuy

.github/workflows/libc-fullbuild-tests.yml

@@ -19,13 +19,20 @@ jobs:
         include:
           - os: ubuntu-24.04
             ccache-variant: sccache
-            c_compiler: clang-20
-            cpp_compiler: clang++-20
+            c_compiler: clang-21
+            cpp_compiler: clang++-21
+            target: x86_64-unknown-linux-llvm
           # TODO: remove ccache logic when https://github.com/hendrikmuhs/ccache-action/issues/279 is resolved.
           - os: ubuntu-24.04-arm
             ccache-variant: ccache
-            c_compiler: clang-20
-            cpp_compiler: clang++-20
+            c_compiler: clang-21
+            cpp_compiler: clang++-21
+            target: aarch64-unknown-linux-llvm
+          - os: ubuntu-24.04
+            ccache-variant: ccache
+            c_compiler: clang
+            cpp_compiler: clang++
+            target: x86_64-unknown-uefi-llvm
           # TODO: add back gcc build when it is fixed
           # - c_compiler: gcc
           #   cpp_compiler: g++
@@ -53,7 +60,7 @@ jobs:
       run: |
         wget https://apt.llvm.org/llvm.sh
         chmod +x llvm.sh
-        sudo ./llvm.sh 20
+        sudo ./llvm.sh 21
         sudo apt-get update
         sudo apt-get install -y libmpfr-dev libgmp-dev libmpc-dev ninja-build linux-libc-dev
         sudo ln -sf /usr/include/$(uname -p)-linux-gnu/asm /usr/include/asm
@@ -76,6 +83,7 @@ jobs:
         -DCMAKE_C_COMPILER_LAUNCHER=${{ matrix.ccache-variant }}
         -DCMAKE_CXX_COMPILER_LAUNCHER=${{ matrix.ccache-variant }}
         -DCMAKE_INSTALL_PREFIX=${{ steps.strings.outputs.build-install-dir }}
+        -DLLVM_RUNTIMES_TARGET=${{ matrix.target }}
         -DLLVM_ENABLE_RUNTIMES="libc;compiler-rt"
         -DLLVM_LIBC_FULL_BUILD=ON
         -DLLVM_LIBC_INCLUDE_SCUDO=ON
@@ -93,6 +101,8 @@ jobs:
         --target install
 
     - name: Test
+      # Skip UEFI tests until we have testing set up.
+      if: ${{ ! endsWith(matrix.target, '-uefi-llvm') }}
       run: >
         cmake 
         --build ${{ steps.strings.outputs.build-output-dir }}