Enable OpenACC GCN testing.

Enable OpenACC GCN testing.

2019-12-03  Andrew Stubbs  <ams@codesourcery.com>

	libgomp/
	* testsuite/lib/libgomp.exp (offload_target_to_openacc_device_type):
	Recognize amdgcn.
	(check_effective_target_openacc_amdgcn_accel_present): New proc.
	(check_effective_target_openacc_amdgcn_accel_selected): New proc.
	* testsuite/libgomp.oacc-c++/c++.exp: Add support for amdgcn.
	* testsuite/libgomp.oacc-c/c.exp: Likewise.
	* testsuite/libgomp.oacc-fortran/fortran.exp: Likewise.

From-SVN: r278935