FS-6293: fix mod_rtmp srcdir build

src/mod/endpoints/mod_rtmp/Makefile.am

@@ -3,6 +3,6 @@ MODNAME=mod_rtmp
 mod_LTLIBRARIES = mod_rtmp.la
 mod_rtmp_la_SOURCES  = mod_rtmp.c rtmp_sig.c rtmp.c rtmp_tcp.c
 mod_rtmp_la_SOURCES += libamf/src/amf0.c libamf/src/hash.c libamf/src/io.c libamf/src/ptrarray.c libamf/src/types.c 
-mod_rtmp_la_CFLAGS   = $(AM_CFLAGS) -Ilibamf/src
+mod_rtmp_la_CFLAGS   = $(AM_CFLAGS) -Ilibamf/src -I$(abs_srcdir)/libamf/src
 mod_rtmp_la_LIBADD   = $(switch_builddir)/libfreeswitch.la
 mod_rtmp_la_LDFLAGS  = -avoid-version -module -no-undefined -shared