[compiler-rt] Use --standalone when running tests on the iOS simulator

We can use `simctl spawn --standalone` to enable running tests without
the need for an already-booted simulator instance.  This also side-steps
the problem of not having a good place to shutdown the instance after
we are finished with testing.

rdar://58118442

Reviewed By: delcypher

Differential Revision: https://reviews.llvm.org/D78409

compiler-rt/test/sanitizer_common/ios_commands/iossim_prepare.py

@@ -1,18 +1,5 @@
 #!/usr/bin/python
 
 import json
-import os
-import subprocess
-
-
-device_id = os.environ.get('SANITIZER_IOSSIM_TEST_DEVICE_IDENTIFIER')
-if not device_id:
-    raise EnvironmentError('Specify SANITIZER_IOSSIM_TEST_DEVICE_IDENTIFIER to select which simulator to use.')
-
-DEVNULL = open(os.devnull, 'w')
-subprocess.call(['xcrun', 'simctl', 'shutdown', device_id], stderr=DEVNULL)
-subprocess.check_call(['xcrun', 'simctl', 'boot', device_id])
-# TODO(rdar58118442): we start the simulator here, but we never tear it down
-
 
 print(json.dumps({"env": {}}))

compiler-rt/test/sanitizer_common/ios_commands/iossim_run.py

@@ -29,7 +29,7 @@
   # We use `shell=True` so that any wildcard globs get expanded by the shell.
   exitcode = subprocess.call(rm_cmd_line_str, shell=True)
 else:
-  exitcode = subprocess.call(["xcrun", "simctl", "spawn", device_id] + sys.argv[1:])
+  exitcode = subprocess.call(["xcrun", "simctl", "spawn", "--standalone", device_id] + sys.argv[1:])
 if exitcode > 125:
   exitcode = 126
 sys.exit(exitcode)