Use PKG_CHECK_MODULES to link libavutil

Without this, when I was building ffms2 and when ffmpeg wasn't installed on the system on ubuntu (in /usr/lib), it was failing to build.

Author: moi15moi

Makefile.am

@@ -59,7 +59,7 @@ src_index_ffmsindex_SOURCES = src/index/ffmsindex.cpp
 if WINDOWS
 src_index_ffmsindex_LDFLAGS = -municode
 endif
-src_index_ffmsindex_LDADD = -lavutil src/core/libffms2.la
+src_index_ffmsindex_LDADD = @AVUTIL_LIBS@ src/core/libffms2.la
 
 .PHONY: test test-build test-clean test-sync test-run
 clean-local: test-clean

configure.ac

@@ -91,6 +91,7 @@ pkgconfigdir="\$(libdir)/pkgconfig"
 AC_SUBST(pkgconfigdir)
 
 PKG_CHECK_MODULES(FFMPEG, [libavformat >= 61.7.0 libavcodec >= 61.19.0 libswscale >= 8.3.0 libavutil >= 59.39.0 libswresample >= 5.3.0])
+PKG_CHECK_MODULES([AVUTIL], [libavutil >= 59.39.0])
 
 dnl As of 0eec06ed8747923faa6a98e474f224d922dc487d ffmpeg only adds -lrt to lavc's
 dnl LIBS, but lavu needs it, so move it to the end if it's present