fix amr build

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@4653 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/mod/codecs/mod_amr/Makefile

 BASE=../../../..
 
-LOCAL_INSERT_CFLAGS=if test -d $(BASE)/libs/amr; then echo "-I$(PREFIX)/include/amr" ; else echo "-DAMR_PASSTHROUGH" ; fi ;
-LOCAL_INSERT_LDFLAGS=test ! -d $(BASE)/libs/amp || echo "-lamr"
+AMR_DIR=$(BASE)/libs/amr
+AMR_A=$(AMR_DIR)/libamr.a
+
+LOCAL_INSERT_CFLAGS=if test -d $(AMR_DIR); then echo "-I$(AMR_DIR)" ; else echo "-DAMR_PASSTHROUGH" ; fi ;
+LOCAL_INSERT_LDFLAGS=test ! -d $(AMR_DIR) || echo "$(AMR_A)";
+
 
 include $(BASE)/build/modmake.rules