Use SWIFT_HOME environment variable instead of hardcoded path

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@5479 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/mod/asr_tts/mod_cepstral/Makefile

-LOCAL_INSERT_LDFLAGS=if test $$osarch = "Darwin" ; then echo "-framework swift" ; else echo "-L/opt/swift/lib -lswift -lceplex_us -lceplang_en -lm" ; fi ;
+LOCAL_INSERT_LDFLAGS=if test $$osarch = "Darwin" ; then echo "-framework swift" ; else echo "-L$(SWIFT_HOME)/lib -lswift -lceplex_us -lceplang_en -lm" ; fi ;
 
-LOCAL_INSERT_CFLAGS=test $$osarch = "Darwin" || echo "-I/opt/swift/include";
+LOCAL_INSERT_CFLAGS=test $$osarch = "Darwin" || echo "-I$(SWIFT_HOME)/include";
 LOCAL_CFLAGS=-w
 include ../../../../build/modmake.rules