ldd: make try_trace more robust and portable

ldd: make try_trace more robust and portable

It was noted in 2005 (BZ #832), 2006 (BZ #3266), and 2007 [1] that ldd
fails on shells other than Bash >= 3.0 because of the pipefail option
around try_trace (added on 2004-12-08).  EGLIBC was patched in 2008 [2]
(r6912) to make the pipefail check run only on shells that support it,
but RTLD output would still be lost on other shells with certain SELinux
policies.

This patch rewrites try_trace to work on any POSIX-conformant shell in
such a way as to also work with such SELinux policies.  It also obviates
one difference between glibc and EGLIBC.

URL: https://sourceware.org/ml/libc-alpha/2007-01/msg00041.html
URL: http://www.eglibc.org/archives/patches/msg00526.html

2013-09-11  P. J. McDermott  <pj@pehjota.net>

	[BZ #832]
	* elf/ldd.bash.in (try_trace): More robustly and portably work around
	SELinux terminal write permissions by using a command substitution
	instead of a pipeline and pipefail option.