[arm] Fix architecture selection when building libatomic with automatic FPU selection

[arm] Fix architecture selection when building libatomic with automatic FPU selection

Libatomic builds a few functions for Arm with an explicit -march
option.  This option does not specify an FPU, which can lead to
problems when targeting a hard-float or softfp environment since the
architecture appears to be incompatible with the selected ABI.

The fix is simple enough, just add +fp (the minimum floating point
option) to the architecture.  We don't use anything from the FP
architecture, so it shouldn't really change anything; and if we are
building for -mfloat-abi=soft the canonicalization process will remove
the unnecessary fp attributes anyway.

	* Makefile.am: (IFUNC_OPTIONS): Set the architecture to
	-march=armv7-a+fp on Linux/Arm.
	* Makefile.in: Regenerated.

From-SVN: r253935