[Bug testsuite/81626] New: Need effective target omp_target

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81626

            Bug ID: 81626
           Summary: Need effective target omp_target
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: testsuite
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

When we build a compiler with nvptx accelerator for openacc testing and test
libgomp, we run into 308 FAIL/UNRESOLVED like this:
...
FAIL: libgomp.fortran/target8.f90   -Os  (test for excess errors)
UNRESOLVED: libgomp.fortran/target8.f90   -Os  compilation failed to produce
executable
...

The failure in more detail is a missing symbol __nvptx_uni:
...
unresolved symbol __nvptx_uni
collect2: error: ld returned 1 exit status
mkoffload: fatal error: x86_64-none-linux-gnu-accel-nvptx-none-gcc returned 1
exit status
compilation terminated.
...

In order to run openmp nvptx offloading test, we need to compile all nvptx code
with -mgomp. Compiling libgcc with -mgomp provides the missing symbol.

Since the compiler as we configure it for openacc testing does not provide any
multilibs with -mgomp, openmp nvptx offloading testing is not supported. 

If we add an effective target that tests if openmp offloading testing is
supported, then we can use it to report UNSUPPORTED instead of FAIL/UNRESOLVED.