ltmain.in: Handle trailing slashes on install commands

A command like:

libtool --mode=install /usr/bin/install -c gck-roots-store-standalone.la
'/image/usr/lib/gnome-keyring/standalone/'

where the path ends with a trailing slash currently fails. This occurs in
software like gnome-keyring or pulseaudio and is because the comparision
code doesn't see the paths as equal. Strip both paths to ensure this works
reliably.

* build-aux/ltmain.in: Strip trailing slashes on install commands.
* NEWS: Update.

NEWS

@@ -21,6 +21,8 @@ NEWS - list of user-visible changes between releases of GNU Libtool
 
   - Fix linking libraries at runtime with tcc by adding run path.
 
+  - Fix path comparison by removing trailing slashes on install commands.
+
 ** Changes in supported systems or compilers:
 
   - Support additional flang-based compilers, 'f18' and 'f95'.

build-aux/ltmain.in

@@ -2405,8 +2405,15 @@ func_mode_install ()
 	func_append dir "$objdir"
 
 	if test -n "$relink_command"; then
+	  # Strip any trailing slash from the destination.
+	  func_stripname '' '/' "$libdir"
+	  destlibdir=$func_stripname_result
+
+	  func_stripname '' '/' "$destdir"
+	  s_destdir=$func_stripname_result
+
 	  # Determine the prefix the user has applied to our future dir.
-	  inst_prefix_dir=`$ECHO "$destdir" | $SED -e "s%$libdir\$%%"`
+	  inst_prefix_dir=`$ECHO "X$s_destdir" | $Xsed -e "s%$destlibdir\$%%"`
 
 	  # Don't allow the user to place us outside of our expected
 	  # location b/c this prevents finding dependent libraries that