LTO: Fix writing of toplevel asm with offloading [PR109816]

When offloading was enabled, top-level 'asm' were added to the offloading
section, confusing assemblers which did not support the syntax. Additionally,
with offloading and -flto, the top-level assembler code did not end up
in the host files.

As r14-321-g9a41d2cdbcd added top-level 'asm' to one libstdc++ header file,
the issue became more apparent, causing fails with nvptx for some
C++ testcases.

	PR libstdc++/109816

gcc/ChangeLog:

	* lto-cgraph.cc (output_symtab): Guard lto_output_toplevel_asms by
	'!lto_stream_offload_p'.

libgomp/ChangeLog:

	* testsuite/libgomp.c++/target-map-class-1.C: New test.
	* testsuite/libgomp.c++/target-map-class-2.C: New test.

(cherry picked from commit a835f046)