Use a non-empty test program to test ability to link.

Use a non-empty test program to test ability to link.

On bare-metal targets, I/O support is typically provided by a BSP and
requires a linker script and/or hosting library to be specified on the
linker command line.  Linking an empty program with the default linker
script may succeed, however, which confuses libstdc++ configuration
when programs that probe for the presence of various I/O features fail
with link errors.

2020-02-12  Sandra Loosemore  <sandra@codesourcery.com>

	PR libstdc++/79193
	PR libstdc++/88999

	config/
	* no-executables.m4: Use a non-empty program to test for linker
	support.

	libgcc/
	* configure: Regenerated.

	libgfortran/
	* configure: Regenerated.

	libiberty/
	* configure: Regenerated.

	libitm/
	* configure: Regenerated.

	libobjc/
	* configure: Regenerated.

	libquadmath/
	* configure: Regenerated.

	libssp/
	* configure: Regenerated.

	libstdc++v-3/
	* configure: Regenerated.