refactor(scripts): clean up bash scripts

script/util/scan-build.sh

@@ -6,17 +6,17 @@ function scan_build {
   # which doesn't support the '-std=c++14' (it is available via '-std=c++1y').
   # Use the system-wide installed clang instead which is 3.5 and does support
   # '-std=c++14'.
-  extra_args+=("--use-analyzer=$(which clang)")
+  extra_args+=("--use-analyzer=$(command -v clang)")
 
   # scan-build will try to guess which CXX should be used to compile the actual
   # code, which is usually g++ but we need g++5 in the CI. Explicitly pass
   # $CC/$CXX to scan-build if they are set in the environment.
 
-  if [[ ! -z "$CC" ]]; then
+  if [[ -n $CC ]]; then
     extra_args+=("--use-cc=$CC")
   fi
 
-  if [[ ! -z "$CXX" ]]; then
+  if [[ -n $CXX ]]; then
     extra_args+=("--use-c++=$CXX")
   fi