[PATCH] Fix ifunc support with DT_TEXTREL segments (BZ#20480)

[Florian Weimer]

* Adhemerval Zanella:

> 	Adam J. Richte  <adam_richter2004@yahoo.com>
> 	Adhemerval Zanella  <adhemerval.zanella@linaro.org>
> 	Fangrui Song  <maskray@google.com>
>
> 	[BZ #20480]
> 	* config.h.in (CAN_TEXTREL_IFUNC): New define.
> 	* configure.ac: Add check if linker supports textrel relocation with
> 	ifunc.
> 	* elf/dl-reloc.c (_dl_relocate_object): Use all required flags on
> 	DT_TEXTREL segments, not only PROT_READ and PROT_WRITE.
> 	* elf/Makefile (ifunc-pie-tests): Add tst-ifunc-textrel.
> 	(CFLAGS-tst-ifunc-textrel.c): New rule.
> 	* elf/tst-ifunc-textrel.c: New file.

The code change looks okay to me.  Not sure about copyright assignment
needs for this one, but it's probably below the threshold because it's
just moving code.

I would prefer if the new test was disabled at the makefile level, not
with a preprocessor conditional.  But it's not a strong preference.

Thanks,
Florian