libgomp: Add testcases for the standard C++ math library on offload targets

libgomp/

	* testsuite/libgomp.c++/target-std__cmath.C: New.
	* testsuite/libgomp.c++/target-std__complex.C: Likewise.
	* testsuite/libgomp.c++/target-std__numbers.C: Likewise.

(cherry picked from commit fbcd0ad41f7cc801664da1e583f6bcad1eb02a08)
3 files changed