Make CC_CODE_COVERAGE_SCRIPT failures fail tests

If you're editing, or overriding, this script and you introduce and
introduce an error, previously this wouldn't fail the test invocation.

Author: keith

tools/test/collect_coverage.sh

@@ -175,7 +175,10 @@ fi
 cd $ROOT
 # Call the C++ code coverage collection script.
 if [[ "$CC_CODE_COVERAGE_SCRIPT" ]]; then
-    eval "${CC_CODE_COVERAGE_SCRIPT}"
+    if ! eval "${CC_CODE_COVERAGE_SCRIPT}"; then
+      echo "error: coverage collection script failed" >&2
+      exit 1
+    fi
 fi
 
 if [[ -z "$LCOV_MERGER" ]]; then