Fix the value of LIBTOOL, as mentioned in the ChangeLog entry.

Author: bhaible

libcharset/m4/libtool.m4

@@ -89,7 +89,7 @@ _LT_SET_OPTIONS([$0], [$1])
 LIBTOOL_DEPS="$ltmain"
 
 # Always use our own libtool.
-LIBTOOL='$(SHELL) $(top_builddir)/libtool'
+LIBTOOL="${CONFIG_SHELL-$SHELL} "'$(top_builddir)/libtool'
 AC_SUBST(LIBTOOL)dnl
 
 _LT_SETUP