Make sure all matrix options are run in libc premerge testing (#146162)

https://github.com/llvm/llvm-project/pull/126315 changes the premerge
testing to build in Debug, Release, and MinSizeRel configs, as opposed
to only MinSizeRel, but for some reason the matrix is not returning all
options now. Fix so that it actually builds the intended configs.

Per discussion in
[146161](https://github.com/llvm/llvm-project/issues/146161), only test
all three configs on Linux x86_64. Other OS's and configurations will
build in Debug mode only.

Also fix a cmake variable and remove outdated comments.

Bug: https://github.com/llvm/llvm-project/issues/146161

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

@@ -15,9 +15,25 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        build_type: [Debug, Release, MinSizeRel]
+        # Build basic linux configuration with Debug/Release/MinSizeRel and all
+        # other configurations in Debug only.
         include:
           - os: ubuntu-24.04
+            build_type: Debug
+            ccache-variant: sccache
+            c_compiler: clang-21
+            cpp_compiler: clang++-21
+            target: x86_64-unknown-linux-llvm
+            include_scudo: ON
+          - os: ubuntu-24.04
+            build_type: Release
+            ccache-variant: sccache
+            c_compiler: clang-21
+            cpp_compiler: clang++-21
+            target: x86_64-unknown-linux-llvm
+            include_scudo: ON
+          - os: ubuntu-24.04
+            build_type: MinSizeRel
             ccache-variant: sccache
             c_compiler: clang-21
             cpp_compiler: clang++-21
@@ -25,12 +41,14 @@ jobs:
             include_scudo: ON
           # TODO: remove ccache logic when https://github.com/hendrikmuhs/ccache-action/issues/279 is resolved.
           - os: ubuntu-24.04-arm
+            build_type: Debug
             ccache-variant: ccache
             c_compiler: clang-21
             cpp_compiler: clang++-21
             target: aarch64-unknown-linux-llvm
             include_scudo: ON
           - os: ubuntu-24.04
+            build_type: Debug
             ccache-variant: ccache
             c_compiler: clang-21
             cpp_compiler: clang++-21
@@ -97,7 +115,7 @@ 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_RUNTIME_TARGETS=${{ matrix.target }} \
         -DLLVM_ENABLE_RUNTIMES="$RUNTIMES" \
         -DLLVM_LIBC_FULL_BUILD=ON \
         -G Ninja \

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

@@ -16,7 +16,7 @@ jobs:
       # Set fail-fast to false to ensure that feedback is delivered for all matrix combinations.
       fail-fast: false
       matrix:
-        build_type: [Debug, Release, MinSizeRel]
+        os: [ubuntu-24.04, ubuntu-24.04-arm, windows-2022, windows-2025, macos-14]
         include:
           # TODO: add linux gcc when it is fixed
           - os: ubuntu-24.04
@@ -96,7 +96,7 @@ jobs:
         cmake -B ${{ steps.strings.outputs.build-output-dir }}
         -DCMAKE_CXX_COMPILER=${{ matrix.compiler.cpp_compiler }}
         -DCMAKE_C_COMPILER=${{ matrix.compiler.c_compiler }}
-        -DCMAKE_BUILD_TYPE=${{ matrix.build_type }}
+        -DCMAKE_BUILD_TYPE=Debug
         -DCMAKE_C_COMPILER_LAUNCHER=${{ matrix.ccache-variant }}
         -DCMAKE_CXX_COMPILER_LAUNCHER=${{ matrix.ccache-variant }}
         -DCMAKE_POLICY_DEFAULT_CMP0141=NEW
@@ -110,7 +110,6 @@ jobs:
         cmake 
         --build ${{ steps.strings.outputs.build-output-dir }} 
         --parallel 
-        --config MinSizeRel 
         --target libc
 
     - name: Test