re PR target/65286 (When building on powerpc64le-unknown-linux-gnu, --disable-multili...

re PR target/65286 (When building on powerpc64le-unknown-linux-gnu, --disable-multilib must be used)

	PR target/65286
	* config.gcc (powerpc*-*-linux*): Arrange for powerpc64le-linux
	to be single-arch by default.  Set cpu_is_64bit for powerpc64
	given --with-cpu=native.
	* config/rs6000/t-fprules: Do not set default MULTILIB vars.
	* config/rs6000/t-linux (MULTIARCH_DIRNAME): Support powerpc64
	and powerpc64le.
	* config/rs6000/linux64.h (SUBSUBTARGET_OVERRIDE_OPTIONS): Test
	rs6000_isa_flags rather than TARGET_64BIT.

From-SVN: r221288