[PATCH], Add support for --with-advance-toolchain=<xx> to PowerPC

[Michael Meissner <meissner at linux dot vnet dot ibm dot com>]

This is a convenience patch that would help those of us who work on the main
GCC releases as well as backporting changes to the IBM Advance Toolchain.  It
adds a new configuration switch, --with-advance-toolchain=<xxx> that configures
the compiler to use the include files, libraries, and dynamic loader that are
released with the IBM Advance Toolchain releases instead of the distribution
headers and libraries.

On the older systems, the distribution glibc (based on glibc 2.11) accounts for
some errors in the testsuite that are fixed in newer glibc's that the Advance
Toolchain provides (Advance Toolchain 7.0 provides 2.18, while Advance
Toolchain 8.0 provides 2.20), and it is useful not to encounter these when
running make check.

I've tested these patches on a power7 SuSE Sles 11.3 big endian system, and on
a power8 Ubuntu little endian system.  On the older system, I can't build a
bootstrap compiler, due to C++ library issues.  On the Ubunto system, I get no
regressions.  Given this switch is a debug convenience option that users are
not expected to use, I don't see the no bootstrap issue as being a problem.

In addition to the trunk, I would like to backport the patch to the active
branches (4.9 and 5).  Is this patch acceptable to commit to the trunk and to
the branches?

2015-06-02  Michael Meissner  <meissner@linux.vnet.ibm.com>

	* config.gcc (powerpc*-*-*): Add support for a new configure
	option --with-advance-toolchain=<xxx> which overrides using the
	default header files, libraries and dynamic linker.

	* config/rs6000/linux64.h (SUBSUBTARGET_EXTRA_SPECS): Add new
	specs to support the configure --with-advance-toolchain=<xxx>
	option.
	(INCLUDE_EXTRA_SPEC): Likewise.
	(LINK_OS_EXTRA_SPEC32): Likewise.
	(LINK_OK_EXTRA_SPEC64): Likewise.
	(LINK_OS_NEW_DTAGS_SPEC): Likewise.
	(DYNAMIC_LINKER_PREFIX): Likewise.
	(CPP_OS_DEFAULT_SPEC): Use the new specs for providing advance
	toolchain support.
	(GLIBC_DYNAMIC_LINKER32): Likewise.
	(GLIBC_DYNAMIC_LINKER64): Likewise.
	(LINK_OS_LINUX_SPEC32): Likewise.
	(LINK_OS_LINUX_SPEC64): Likewise.

	* doc/install.texi (--enable-advance-toolchain=<xx>): Document new
	configuration option.

-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.vnet.ibm.com, phone: +1 (978) 899-4797

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