[OpenMP][DeviceRTL] Add the support for printf in a freestanding way

For NVPTX, `printf` can be used just with a function declaration. For AMDGCN, an
function definition is added, but it simply returns.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D109728

GitOrigin-RevId: af4599b8abcaff02450449a22a7206dbb694b952
1 file changed