Simplify strict updatability linting error message

Throwing a RuntimeError leads to a stack trace in the build failure
error message, which is not useful and makes the error harder to
understand.

Bug: 320698986
Test: Presubmits
Change-Id: I0b79185fff7b9c8d4085b23936b80b3d026a4384
diff --git a/scripts/lint_project_xml.py b/scripts/lint_project_xml.py
index 3b0158d..c40b07d 100755
--- a/scripts/lint_project_xml.py
+++ b/scripts/lint_project_xml.py
@@ -18,6 +18,7 @@
 """This file generates project.xml and lint.xml files used to drive the Android Lint CLI tool."""
 
 import argparse
+import sys
 from xml.dom import minidom
 
 from ninja_rsp import NinjaRspFileReader
@@ -159,8 +160,8 @@
   if args.baseline_path:
     baseline = minidom.parse(args.baseline_path)
     disallowed_issues = check_baseline_for_disallowed_issues(baseline, args.disallowed_issues)
-    if bool(disallowed_issues):
-      raise RuntimeError('disallowed issues %s found in lint baseline file %s for module %s'
+    if disallowed_issues:
+      sys.exit('disallowed issues %s found in lint baseline file %s for module %s'
                          % (disallowed_issues, args.baseline_path, args.name))
 
   if args.project_out: