Detect and disable openmp tests that require multiple hardware processor to run when only one core is available.

[serge-sans-paille]

Summary

Team tests seem to require at least two physical cores, and using the same trick as in https://reviews.llvm.org/D55598 doesn't work (why?) .
Using lit configuration instead.

[jdoerfert]

I am fairly certain we need this lit.cfg addition soon anyway, so I'm OK with this, @AndreyChurbanov any objections?

[AndreyChurbanov]

LGTM

We may need to also loose the internal tough limit of number of threads in the teams construct, which is currently not convenient to overcome. But this needs time to work on..

openmp/runtime/test/lit.cfg

if 'Linux' in config.operating_system:
     config.available_features.add("linux")
 
 if config.operating_system == 'NetBSD':
     config.available_features.add("netbsd")
 
 if config.operating_system in ['Linux', 'Windows']:
     config.available_features.add('affinity')
 
+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
 if 'INTEL_LICENSE_FILE' in os.environ:
     config.environment['INTEL_LICENSE_FILE'] = os.environ['INTEL_LICENSE_FILE']
 
 
 # substitutions
 config.substitutions.append(("%libomp-compile-and-run", \
     "%libomp-compile && %libomp-run"))

openmp/runtime/test/ompt/teams/parallel_team.c

 // RUN: %libomp-compile-and-run | %sort-threads | FileCheck %s
-// REQUIRES: ompt
+// REQUIRES: ompt, multicpu
 // UNSUPPORTED: gcc
 #include "callback.h"
 
 int main() {
 #pragma omp target teams num_teams(1) thread_limit(2)
 #pragma omp parallel num_threads(2)
   { printf("In teams\n"); }
   return 0;

openmp/runtime/test/ompt/teams/serial_teams.c

 // RUN: %libomp-compile-and-run | %sort-threads | FileCheck %s
-// REQUIRES: ompt
+// REQUIRES: ompt, multicpu
 // UNSUPPORTED: gcc
 #include "callback.h"
 
 int main() {
 #pragma omp target teams num_teams(2) thread_limit(1)
 #pragma omp parallel num_threads(1)
   { printf("In teams parallel\n"); }
   return 0;