Bug 1798660 - Drive-by: Use a better test for IsInDir. r=gsvelto

Differential Revision: https://phabricator.services.mozilla.com/D163301

toolkit/crashreporter/tools/symbolstore.py

@@ -314,10 +314,11 @@ else:
 
 
 def IsInDir(file, dir):
-    # the lower() is to handle win32+vc8, where
-    # the source filenames come out all lowercase,
-    # but the srcdir can be mixed case
-    return os.path.abspath(file).lower().startswith(os.path.abspath(dir).lower())
+    try:
+        Path(file).relative_to(dir)
+        return True
+    except ValueError:
+        return False
 
 
 def GetVCSFilenameFromSrcdir(file, srcdir):