Use LIBS iso. LDFLAGS when compiling conftest

Author: Erlend E. Aasland

configure

@@ -3521,7 +3521,7 @@ AS_VAR_IF([found_tcltk], [no], [
 
 WITH_SAVE_ENV([
   CPPFLAGS="$TCLTK_CFLAGS $CFLAGS"
-  LDFLAGS="$TCLTK_LIBS $LDFLAGS"
+  LIBS="$TCLTK_LIBS $LDFLAGS"
 
   AC_LINK_IFELSE([
     AC_LANG_PROGRAM([