chromaprint: use ffmpeg pg

audio/chromaprint/Portfile

@@ -3,6 +3,7 @@
 PortSystem          1.0
 PortGroup           cmake 1.1
 PortGroup           github 1.0
+PortGroup           ffmpeg 1.0
 
 github.setup        acoustid chromaprint 1.6.0 v
 github.tarball_from archive
@@ -25,14 +26,13 @@ checksums           rmd160  420e21f6ab10ba3e06536cb3bef60948dbb12f1f \
 
 compiler.cxx_standard 2011
 
-set ffmpeg_ver      8
+ffmpeg.version      8
 
-depends_lib-append      port:ffmpeg${ffmpeg_ver} \
-                        port:zlib
+depends_lib-append      port:zlib
 
 configure.args-append   -DBUILD_TESTS=OFF \
                         -DBUILD_TOOLS=ON \
-                        -DFFMPEG_ROOT=${prefix}/libexec/ffmpeg${ffmpeg_ver}
+                        -DFFMPEG_ROOT=${ffmpeg.prefix}
 
 variant tests description {Enable tests} {
     configure.args-replace \