build: Add component for the SRTP common code

This allows expressing the SRTP test code dependencies more clearly.

configure

@@ -1700,6 +1700,7 @@ CONFIG_EXTRA="
     rv34dsp
     sinewin
     snappy
+    srtp
     startcode
     texturedsp
     texturedspenc
@@ -2257,7 +2258,7 @@ ogg_demuxer_select="dirac_parse"
 opus_muxer_select="ogg_muxer"
 psp_muxer_select="mov_muxer"
 rtp_demuxer_select="sdp_demuxer"
-rtpdec_select="asf_demuxer jpegtables mov_demuxer mpegts_demuxer rm_demuxer rtp_protocol"
+rtpdec_select="asf_demuxer jpegtables mov_demuxer mpegts_demuxer rm_demuxer rtp_protocol srtp"
 rtsp_demuxer_select="http_protocol rtpdec"
 rtsp_muxer_select="rtp_muxer http_protocol rtp_protocol rtpenc_chain"
 sap_demuxer_select="sdp_demuxer"
@@ -2330,7 +2331,7 @@ rtmpts_protocol_select="ffrtmphttp_protocol https_protocol"
 rtp_protocol_select="udp_protocol"
 sctp_protocol_deps="struct_sctp_event_subscribe"
 sctp_protocol_select="network"
-srtp_protocol_select="rtp_protocol"
+srtp_protocol_select="rtp_protocol srtp"
 tcp_protocol_select="network"
 tls_gnutls_protocol_deps="gnutls"
 tls_gnutls_protocol_select="tcp_protocol"

libavformat/Makefile

@@ -54,9 +54,9 @@ OBJS-$(CONFIG_RTPDEC)                    += rdt.o                       \
                                             rtpdec_svq3.o               \
                                             rtpdec_vp8.o                \
                                             rtpdec_vp9.o                \
-                                            rtpdec_xiph.o               \
-                                            srtp.o
+                                            rtpdec_xiph.o
 OBJS-$(CONFIG_RTPENC_CHAIN)              += rtpenc_chain.o rtp.o
+OBJS-$(CONFIG_SRTP)                      += srtp.o
 
 # muxers/demuxers
 OBJS-$(CONFIG_A64_MUXER)                 += a64.o rawenc.o
@@ -416,12 +416,12 @@ SKIPHEADERS-$(CONFIG_FFRTMPCRYPT_PROTOCOL) += rtmpdh.h
 SKIPHEADERS-$(CONFIG_NETWORK)            += network.h rtsp.h
 
 TESTPROGS = seek                                                        \
-            srtp                                                        \
             url                                                         \
 
 TESTPROGS-$(CONFIG_MOV_MUXER)            += movenc
 TESTPROGS-$(CONFIG_NETWORK)              += noproxy
 TESTPROGS-$(CONFIG_FFRTMPCRYPT_PROTOCOL) += rtmpdh
+TESTPROGS-$(CONFIG_SRTP)                 += srtp
 
 TOOLS     = aviocat                                                     \
             ismindex                                                    \