Shellcheck warnings addressed

SC2236: use [[ -n "$var" ]] instead of [[ ! -z "$var" ]]
SC2035: use -- end of options, to accomodate filename w\ hyphens
SC2155: `local -r var=..` for readonly variable shellcheck ignores return value masking
SC2045: prefer glob to iteration over `ls`

Bug: N/A
Test: ran ./run_intergration_tests.sh
Change-Id: Iaf313857ecc417e855afd70c7455841b54b1c363
diff --git a/tests/bp2build_bazel_test.sh b/tests/bp2build_bazel_test.sh
index 78ddced..3cdf6aa 100755
--- a/tests/bp2build_bazel_test.sh
+++ b/tests/bp2build_bazel_test.sh
@@ -11,10 +11,10 @@
 function test_bp2build_null_build() {
   setup
   run_soong bp2build
-  local output_mtime1=$(stat -c "%y" out/soong/bp2build_workspace_marker)
+  local -r output_mtime1=$(stat -c "%y" out/soong/bp2build_workspace_marker)
 
   run_soong bp2build
-  local output_mtime2=$(stat -c "%y" out/soong/bp2build_workspace_marker)
+  local -r output_mtime2=$(stat -c "%y" out/soong/bp2build_workspace_marker)
 
   if [[ "$output_mtime1" != "$output_mtime2" ]]; then
     fail "Output bp2build marker file changed on null build"
@@ -36,10 +36,10 @@
   touch foo/bar/a.txt foo/bar/b.txt
 
   run_soong bp2build
-  local output_mtime1=$(stat -c "%y" out/soong/bp2build_workspace_marker)
+  local -r output_mtime1=$(stat -c "%y" out/soong/bp2build_workspace_marker)
 
   run_soong bp2build
-  local output_mtime2=$(stat -c "%y" out/soong/bp2build_workspace_marker)
+  local -r output_mtime2=$(stat -c "%y" out/soong/bp2build_workspace_marker)
 
   if [[ "$output_mtime1" != "$output_mtime2" ]]; then
     fail "Output bp2build marker file changed on null build"
@@ -147,10 +147,10 @@
   run_soong bp2build
 
   run_bazel build --package_path=out/soong/workspace //a:qq
-  local output_mtime1=$(stat -c "%y" bazel-bin/a/_objs/qq/qq.o)
+  local -r output_mtime1=$(stat -c "%y" bazel-bin/a/_objs/qq/qq.o)
 
   run_bazel build --package_path=out/soong/workspace //a:qq
-  local output_mtime2=$(stat -c "%y" bazel-bin/a/_objs/qq/qq.o)
+  local -r output_mtime2=$(stat -c "%y" bazel-bin/a/_objs/qq/qq.o)
 
   if [[ "$output_mtime1" != "$output_mtime2" ]]; then
     fail "output changed on null build"
@@ -161,7 +161,7 @@
 EOF
 
   run_bazel build --package_path=out/soong/workspace //a:qq
-  local output_mtime3=$(stat -c "%y" bazel-bin/a/_objs/qq/qq.o)
+  local -r output_mtime3=$(stat -c "%y" bazel-bin/a/_objs/qq/qq.o)
 
   if [[ "$output_mtime1" == "$output_mtime3" ]]; then
     fail "output not changed when included header changed"