Don't reset LTDLINCL unless we're using an external libltdl

installation. 

This commit was SVN r23192.

opal/config/opal_setup_libltdl.m4

@@ -34,7 +34,6 @@ AC_DEFUN([OPAL_SETUP_LIBLTDL],[
     # $enable_shared and $enable_static and pass down the corresponding
     # flags.
 
-    LTDLINCL=
     LIBLTDL=
     LIBLTDL_SUBDIR=
     OPAL_HAVE_LTDL_ADVISE=0
@@ -66,6 +65,10 @@ AC_DEFUN([OPAL_SETUP_LIBLTDL],[
               ;;
            external)
               AC_MSG_RESULT([external copy (unspecified)])
+              # If we're using an extern libltdl, then reset the
+              # LTDLINCL that was set earlier (ie., there's no need to
+              # -I into our internal libltdl tree).
+              LDTLINCL=
               libltdl_location=
               libltdl_need_external=1
               ;;
@@ -73,6 +76,10 @@ AC_DEFUN([OPAL_SETUP_LIBLTDL],[
               AC_MSG_RESULT([external copy ($libltdl_location)])
               OMPI_CHECK_WITHDIR([libltdl], [$libltdl_location], 
                                  [include/ltdl.h])
+              # If we're using an extern libltdl, then reset the
+              # LTDLINCL that was set earlier (ie., there's no need to
+              # -I into our internal libltdl tree).
+              LDTLINCL=
               libltdl_need_external=1
               ;;
             esac