[PATCH] PR dynamic-link/17711: copy relocations against protected symbols don't work

[Roland McGrath]

> Protocted symbol in shared library can only be accessed from PIE
> or shared library.  Linker in binutils 2.26 enforces it.  We must
> compile vismain with -fPIE and link it with -pie.  OK for master?

Add some comments (in vismain.c is probably fine) explaining that it must
be a PIE and why.

> 	PR dynamic-link/17711
	[BZ #17711]

> 	* elf/Makefile (tests): Add vismain only if PIE is enabled.
> 	(tests-pie): Add vismain.
> 	(CFLAGS-vismain.c): New.