Revert "[openmp] [test] Set __COMPAT_LAYER=RunAsInvoker when running tests on Windows"

[mstorsjo]

Summary

This reverts commit 63f0fdc2628dfb2f52ed5a92e579f99261d946ed.

Since f1431bbfb17cd7167adda9fc8521bb6eec52c300, this environment
variable is always set up by lit itself, so individual test suites
don't need to set it.

[alvinhochun]

LGTM

openmp/runtime/test/lit.cfg

if config.operating_system in ['Linux']:
     config.available_features.add('hidden-helper')
 
 target_arch = getattr(config, 'target_arch', None)
 if target_arch:
   config.available_features.add(target_arch + '-target-arch')
   if target_arch in ['x86_64', 'i386']:
     config.available_features.add('x86-target-arch')
 
-# Avoid Windows heuristics which try to detect potential installer programs
-# (which may need to run with elevated privileges) and ask if the user wants
-# to run them in that way. This heuristic may match for executables containing
-# the word "patch" which is a substring of "dispatch". Set an environment
-# variable indicating that we want to execute them with the current user.
-if config.operating_system == 'Windows':
-    config.environment['__COMPAT_LAYER'] = 'RunAsInvoker'
-
 import multiprocessing
 try:
     if multiprocessing.cpu_count() > 1:
         config.available_features.add('multicpu')
 except NotImplementedError:
     pass
 
 # to run with icc INTEL_LICENSE_FILE must be set