libiberty: fix --enable-install-libiberty flag [PR 56780]

Commit 199570 fixed the --disable-install-libiberty behavior, but it also
added a bug where the enable path never works because the initial clear
of target_header_dir wasn't deleted.  So we end up initializing properly
at the top only to reset it at the end all the time.

From-SVN: r206367

libiberty/ChangeLog

+2014-01-06  Mike Frysinger  <vapier@gentoo.org>
+
+	PR other/56780
+	* configure.ac: Delete target_header_dir assignment.
+	* configure: Regenerated.
+
 2014-01-06  Gary Benson  <gbenson@redhat.com>
 
 	* cp-demangle.c (struct d_print_info): New fields

libiberty/configure

@@ -5510,7 +5510,6 @@ fi
 
 setobjs=
 CHECK=
-target_header_dir=
 if test -n "${with_target_subdir}"; then
 
   # We are being configured as a target library.  AC_REPLACE_FUNCS

libiberty/configure.ac

@@ -411,7 +411,6 @@ fi
 
 setobjs=
 CHECK=
-target_header_dir=
 if test -n "${with_target_subdir}"; then
 
   # We are being configured as a target library.  AC_REPLACE_FUNCS