Fix runner arch

Author: tstellar

.github/workflows/premerge.yaml

@@ -70,7 +70,7 @@ jobs:
           export CC=/opt/llvm/bin/clang
           export CXX=/opt/llvm/bin/clang++
 
-          if "$RUNNER_ARCH" = "ARM64"; then
+          if [ "$RUNNER_ARCH" = "ARM64" ]; then
             # XFAIL lldb test: https://github.com/llvm/llvm-project/issues/155895
             export LIT_XFAIL="functionalities/gdb_remote_client/TestqOffsets.py"
             export LIT_FILTER_OUT=TestqOffsets.py