Fix libgomp build on targets that are not Linux-based or accelerators

Fix libgomp build on targets that are not Linux-based or accelerators

The patch 'openmp: Add support for the 'indirect' clause in C/C++'
introduced a new file target-indirect.c into the Makefile sources,
but that file was only present in config/linux/ and config/accel/,
so targets that are not Linux-based or GPU accelerators will not
pick it up and fail to build.

This is fixed by making the version in config/linux/ the default by
moving it into the base directory of libgomp.

2023-11-07  Kwok Cheung Yeung  <kcy@codesourcery.com>

	libgomp/
	* config/linux/target-indirect.c: Move to...
	* target-indirect.c: ...here.