powerpc musl libc support

powerpc musl libc support

gcc/
	* config/rs6000/linux64.h (MUSL_DYNAMIC_LINKER32): Define.
	(MUSL_DYNAMIC_LINKER64): Define.
	(GNU_USER_DYNAMIC_LINKER32): Update.
	(GNU_USER_DYNAMIC_LINKER64): Update.
	(CHOOSE_DYNAMIC_LINKER): Update.

	* config/rs6000/sysv4.h (GNU_USER_DYNAMIC_LINKER): Update.
	(MUSL_DYNAMIC_LINKER, MUSL_DYNAMIC_LINKER_E,)
	(INCLUDE_DEFAULTS_MUSL_GPP, INCLUDE_DEFAULTS_MUSL_LOCAL,)
	(INCLUDE_DEFAULTS_MUSL_PREFIX, INCLUDE_DEFAULTS_MUSL_CROSS,)
	(INCLUDE_DEFAULTS_MUSL_TOOL, INCLUDE_DEFAULTS_MUSL_NATIVE): Define.
	(CHOOSE_DYNAMIC_LINKER): Update.
	(INCLUDE_DEFAULTS): Redefine.

	* config/rs6000/sysv4le.h (MUSL_DYNAMIC_LINKER_E): Define.

Co-Authored-By: Szabolcs Nagy <szabolcs.nagy@arm.com>
From-SVN: r229266