Convert relative paths to absolute paths in iOS test runner

ios/build/bots/scripts/test_runner.py

Index: ios/build/bots/scripts/test_runner.py
diff --git a/ios/build/bots/scripts/test_runner.py b/ios/build/bots/scripts/test_runner.py
index dd53a182c5901607c060b7d961dcc9f90e42b4c2..2a0c5ef65a4fb102f8d8f0c5288dcd05bcbdfdfe 100644
--- a/ios/build/bots/scripts/test_runner.py
+++ b/ios/build/bots/scripts/test_runner.py
@@ -154,6 +154,7 @@ class TestRunner(object):
       XcodeVersionNotFoundError: If the given Xcode version does not exist.
       XCTestPlugInNotFoundError: If the .xctest PlugIn does not exist.
     """
+    app_path = os.path.abspath(app_path)
     if not os.path.exists(app_path):
       raise AppNotFoundError(app_path)
 
@@ -375,6 +376,7 @@ class SimulatorTestRunner(TestRunner):
         xctest=xctest,
     )
 
+    iossim_path = os.path.abspath(iossim_path)
     if not os.path.exists(iossim_path):
       raise SimulatorNotFoundError(iossim_path)