workflows/release-binaries: Remove unused 'build_flang' variables (#164547)

Author: tstellar

.github/workflows/release-binaries.yml

@@ -141,15 +141,12 @@ jobs:
           target_cmake_flags="$target_cmake_flags -DBOOTSTRAP_BOOTSTRAP_DARWIN_osx_ARCHS=$arches -DBOOTSTRAP_BOOTSTRAP_DARWIN_osx_BUILTIN_ARCHS=$arches"
         fi
 
-        build_flang="true"
-
         if [ "$RUNNER_OS" = "Windows" ]; then
           # The build times out on Windows, so we need to disable LTO.
           target_cmake_flags="$target_cmake_flags -DLLVM_RELEASE_ENABLE_LTO=OFF"
         fi
 
         echo "target-cmake-flags=$target_cmake_flags" >> $GITHUB_OUTPUT
-        echo "build-flang=$build_flang" >> $GITHUB_OUTPUT
         case "${{ inputs.runs-on }}" in
           ubuntu-22.04*)
             build_runs_on="depot-${{ inputs.runs-on }}-16"