Only add `darwin_log_cmd` lit shell test feature when the log can be queried.

[delcypher]

Summary

Follow up fix to 445b810fbd4. The log show command only works for
privileged users so run a quick test of the command during lit config to
see if the command works and only add the darwin_log_cmd feature if
this is the case.

Unfortunately this means the asan/TestCases/Darwin/duplicate_os_log_reports.cpp
test and any other tests in the future that use this feature won't run
for unprivileged users which is likely the case in CI.

rdar://problem/55986279

[delcypher]

@yln Thanks for the review!

compiler-rt/test/lit.common.cfg.py

 
 config.default_sanitizer_opts = []
 if config.host_os == 'Darwin':
   # On Darwin, we default to `abort_on_error=1`, which would make tests run
   # much slower. Let's override this and run lit tests with 'abort_on_error=0'.
   config.default_sanitizer_opts += ['abort_on_error=0']
   config.default_sanitizer_opts += ['log_to_syslog=0']
   if lit.util.which('log'):
+    # Querying the log can only done by a privileged user so
+    # so check if we can query the log.
+    exit_code = -1
+    with open('/dev/null', 'r') as f:
+      # Run a `log show` command the should finish fairly quickly and produce very little output.
+      exit_code = subprocess.call(['log', 'show', '--last', '1m', '--predicate', '1 == 0'], stdout=f, stderr=f)
+    if exit_code == 0:
       config.available_features.add('darwin_log_cmd')
     else:
+      lit_config.warning('log command found but cannot queried')
+  else:
     lit_config.warning('log command not found. Some tests will be skipped.')
 elif config.android:
   config.default_sanitizer_opts += ['abort_on_error=0']
 
 # Allow tests to use REQUIRES=stable-runtime.  For use when you cannot use XFAIL
 # because the test hangs or fails on one configuration and not the other.
 if config.android or (config.target_arch not in ['arm', 'armhf', 'aarch64']):
   config.available_features.add('stable-runtime')