Fix bazel coverage false negative

Previously this short circuit meant the tests weren't actually run, and
they would always exit 0, in the case the test rule didn't set the lcov
related attributes.

More context: bazelbuild#13978

Closes bazelbuild#14807.

RELNOTES: Fixed an issue where Bazel could erroneously report a test passes in coverage mode without actually running the test.
PiperOrigin-RevId: 428756211

src/test/shell/bazel/bazel_coverage_starlark_test.sh

@@ -58,6 +58,33 @@ EOF
         || fail "Coverage run failed but should have succeeded."
 }
 
+function test_starlark_rule_without_lcov_merger_failing_test() {
+    cat <<EOF > rules.bzl
+def _impl(ctx):
+    executable = ctx.actions.declare_file(ctx.attr.name)
+    ctx.actions.write(executable, "exit 1", is_executable = True)
+    return [
+        DefaultInfo(
+            executable = executable,
+        )
+    ]
+custom_test = rule(
+    implementation = _impl,
+    test = True,
+)
+EOF
+
+    cat <<EOF > BUILD
+load(":rules.bzl", "custom_test")
+
+custom_test(name = "foo_test")
+EOF
+    if bazel coverage //:foo_test > $TEST_log; then
+      fail "Coverage run succeeded but should have failed."
+    fi
+}
+
+
 function test_starlark_rule_with_custom_lcov_merger() {
 
     cat <<EOF > lcov_merger.sh

tools/test/collect_coverage.sh

@@ -39,7 +39,10 @@ if [[ -z "$LCOV_MERGER" ]]; then
   # it.
   # TODO(cmita): Improve this situation so this early-exit isn't required.
   touch $COVERAGE_OUTPUT_FILE
-  exit 0
+  # Execute the test.
+  "$@"
+  TEST_STATUS=$?
+  exit "$TEST_STATUS"
 fi
 
 function resolve_links() {