Don't clobber LDFLAGS - ensures configure finds libobjc2.
Properly pass -export-dynamic to the linker.

Index: platform.m4
--- platform.m4.orig
+++ platform.m4
@@ -97,7 +97,7 @@ AC_DEFUN(OD_CONFIG_PLUGIN, [
 	    PLUGIN_LD="${CC} -shared"
 	    PLUGIN_LD_FLAGS=""
 	    PLUGIN_SUFFIX=".so"
-	    LDFLAGS="-export-dynamic"
+	    LDFLAGS="-Wl,-export-dynamic ${LDFLAGS}"
 	    ;;
     esac