cros_build_lib: Add root user check helpers

Add helper functions, to check root privilege for the user.

BUG=b:218521368
TEST=run_tests lib/ scripts/ service/ cli/

Change-Id: Idd0ad8be3764b323b140d3e334399eef4d21e8a6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/3491293
Tested-by: Ram Chandrasekar <rchandrasekar@google.com>
Auto-Submit: Ram Chandrasekar <rchandrasekar@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Ram Chandrasekar <rchandrasekar@google.com>
diff --git a/scripts/cros_sysroot_utils.py b/scripts/cros_sysroot_utils.py
index 330436b..d43af01 100644
--- a/scripts/cros_sysroot_utils.py
+++ b/scripts/cros_sysroot_utils.py
@@ -4,11 +4,11 @@
 
 """Collection of tools to create sysroots."""
 
-import os
 import sys
 
 from chromite.lib import commandline
 from chromite.lib import cros_build_lib
+from chromite.lib import osutils
 from chromite.lib import sysroot_lib
 
 
@@ -65,7 +65,7 @@
   if not cros_build_lib.IsInsideChroot():
     raise commandline.ChrootRequiredError(argv)
 
-  if os.geteuid() != 0:
+  if osutils.IsNonRootUser():
     cros_build_lib.sudo_run(sys.argv, print_cmd=False)
     return