config.gcc (powerpc*-linux*-*): Add support for 64-bit little endian Linux systems to optionally enable...

2018-01-16  Michael Meissner  <meissner@linux.vnet.ibm.com>

	* config.gcc (powerpc*-linux*-*): Add support for 64-bit little
	endian Linux systems to optionally enable multilibs for selecting
	the long double type if the user configured an explicit type.
	* config/rs6000/rs6000.h (TARGET_IEEEQUAD_MULTILIB): Indicate we
	have no long double multilibs if not defined.
	* config/rs6000/rs6000.c (rs6000_option_override_internal): Do not
	warn if the user used -mabi={ieee,ibm}longdouble and we built
	multilibs for long double.
	* config/rs6000/linux64.h (MULTILIB_DEFAULTS_IEEE): Define as the
	appropriate multilib option.
	(MULTILIB_DEFAULTS): Add MULTILIB_DEFAULTS_IEEE to the default
	multilib options.
	* config/rs6000/t-ldouble-linux64le-ibm: New configuration files
	for building long double multilibs.
	* config/rs6000/t-ldouble-linux64le-ieee: Likewise.

From-SVN: r256775