libgomp: Fix on_device_arch.c aux-file handling [PR99555]

libgomp/ChangeLog:

	PR target/99555
	* testsuite/lib/on_device_arch.c: Move to ...
	* testsuite/libgomp.c-c++-common/on_device_arch.h: ... here.
	* testsuite/libgomp.fortran/on_device_arch.c: New file;
	#include on_device_arch.h.
	* testsuite/libgomp.c-c++-common/task-detach-6.c: #include
	on_device_arch.h instead of using dg-additional-source.
	* testsuite/libgomp.c/pr99555-1.c: Likewise.
	* testsuite/libgomp.fortran/task-detach-6.f90: Update to use
	on_device_arch.c without relative paths.

libgomp/testsuite/libgomp.c-c++-common/task-detach-6.c

@@ -1,10 +1,8 @@
 /* { dg-do run } */
 
-/* { dg-additional-sources "../lib/on_device_arch.c" } */
-extern int on_device_arch_nvptx ();
-
 #include <omp.h>
 #include <assert.h>
+#include "on_device_arch.h"
 
 /* Test tasks with detach clause on an offload device.  Each device
    thread spawns off a chain of tasks, that can then be executed by

libgomp/testsuite/libgomp.c/pr99555-1.c

@@ -2,8 +2,7 @@
 
 // { dg-additional-options "-O0" }
 
-// { dg-additional-sources "../lib/on_device_arch.c" }
-extern int on_device_arch_nvptx ();
+#include "../libgomp.c-c++-common/on_device_arch.h"
 
 int main (void)
 {

libgomp/testsuite/libgomp.fortran/on_device_arch.c

@@ -0,0 +1,3 @@
+/* Auxiliar file.  */
+/* { dg-do compile  { target skip-all-targets } } */
+#include "../libgomp.c-c++-common/on_device_arch.h"

libgomp/testsuite/libgomp.fortran/task-detach-6.f90

@@ -1,6 +1,6 @@
 ! { dg-do run }
 
-! { dg-additional-sources ../lib/on_device_arch.c }
+! { dg-additional-sources on_device_arch.c }
   ! { dg-prune-output "command-line option '-fintrinsic-modules-path=.*' is valid for Fortran but not for C" }
 
 ! Test tasks with detach clause on an offload device.  Each device