[CI] Prefer Bash Tests over Empty String Comparisons (#168575)

These are more idiomatic in bash.

Author: boomanaiden154

.ci/monolithic-linux.sh

@@ -64,13 +64,13 @@ cmake -S "${MONOREPO_ROOT}"/llvm -B "${BUILD_DIR}" \
 
 start-group "ninja"
 
-if [[ "${targets}" != "" ]]; then
+if [[ -n "${targets}" ]]; then
   # Targets are not escaped as they are passed as separate arguments.
   ninja -C "${BUILD_DIR}" -k 0 ${targets} |& tee ninja.log
   cp ${BUILD_DIR}/.ninja_log ninja.ninja_log
 fi
 
-if [[ "${runtime_targets}" != "" ]]; then
+if [[ -n "${runtime_targets}" ]]; then
   start-group "ninja Runtimes"
 
   ninja -C "${BUILD_DIR}" ${runtime_targets} |& tee ninja_runtimes.log
@@ -79,7 +79,7 @@ fi
 
 # Compiling runtimes with just-built Clang and running their tests
 # as an additional testing for Clang.
-if [[ "${runtime_targets_needs_reconfig}" != "" ]]; then
+if [[ -n "${runtime_targets_needs_reconfig}" ]]; then
   start-group "CMake Runtimes C++26"
 
   cmake \

.ci/monolithic-windows.sh

@@ -51,13 +51,13 @@ cmake -S "${MONOREPO_ROOT}"/llvm -B "${BUILD_DIR}" \
 
 start-group "ninja"
 
-if [[ "${targets}" != "" ]]; then
+if [[ -n "${targets}" ]]; then
   # Targets are not escaped as they are passed as separate arguments.
   ninja -C "${BUILD_DIR}" -k 0 ${targets} |& tee ninja.log
   cp ${BUILD_DIR}/.ninja_log ninja.ninja_log
 fi
 
-if [[ "${runtimes_targets}" != "" ]]; then
+if [[ -n "${runtimes_targets}" ]]; then
   start-group "ninja runtimes"
 
   ninja -C "${BUILD_DIR}" -k 0 ${runtimes_targets} |& tee ninja_runtimes.log

.ci/utils.sh

@@ -33,7 +33,7 @@ function at-exit {
   # If building fails there will be no results files.
   shopt -s nullglob
 
-  if [[ "$GITHUB_ACTIONS" != "" ]]; then
+  if [[ -n "$GITHUB_ACTIONS" ]]; then
     python "${MONOREPO_ROOT}"/.ci/generate_test_report_github.py \
       $retcode "${BUILD_DIR}"/test-results.*.xml "${MONOREPO_ROOT}"/ninja*.log \
       >> $GITHUB_STEP_SUMMARY
@@ -44,7 +44,7 @@ function at-exit {
   fi
 
   if [[ "$retcode" != "0" ]]; then
-    if [[ "$GITHUB_ACTIONS" != "" ]]; then
+    if [[ -n "$GITHUB_ACTIONS" ]]; then
       python "${MONOREPO_ROOT}"/.ci/premerge_advisor_upload.py \
         $(git rev-parse HEAD~1) $GITHUB_RUN_NUMBER \
         "${BUILD_DIR}"/test-results.*.xml "${MONOREPO_ROOT}"/ninja*.log
@@ -59,10 +59,10 @@ trap at-exit EXIT
 
 function start-group {
   groupname=$1
-  if [[ "$GITHUB_ACTIONS" != "" ]]; then
+  if [[ -n "$GITHUB_ACTIONS" ]]; then
     echo "::endgroup"
     echo "::group::$groupname"
-  elif [[ "$POSTCOMMIT_CI" != "" ]]; then
+  elif [[ -n "$POSTCOMMIT_CI" ]]; then
     echo "@@@$STEP@@@"
   else
     echo "Starting $groupname"
@@ -73,6 +73,6 @@ export PIP_BREAK_SYSTEM_PACKAGES=1
 pip install -q -r "${MONOREPO_ROOT}"/.ci/all_requirements.txt
 
 # The ARM64 builders run on AWS and don't have access to the GCS cache.
-if [[ "$GITHUB_ACTIONS" != "" ]] && [[ "$RUNNER_ARCH" != "ARM64" ]]; then
+if [[ -n "$GITHUB_ACTIONS" ]] && [[ "$RUNNER_ARCH" != "ARM64" ]]; then
   python .ci/cache_lit_timing_files.py download
 fi