add flac as a dependency, force audacity to use system libs

.SRCINFO

@@ -1,6 +1,6 @@
 pkgbase = audacity-git
 	pkgdesc = A program that lets you manipulate digital audio waveforms
-	pkgver = 3.1.0.beta.1.r20.g2d5320dd3
+	pkgver = 3.1.0.beta.1.r28.g81bcb372d
 	pkgrel = 1
 	url = https://www.audacityteam.org/
 	arch = i686
@@ -8,35 +8,38 @@ pkgbase = audacity-git
 	groups = pro-audio
 	license = GPL2
 	license = CCPL
-	makedepends = git
 	makedepends = cmake
-	makedepends = gcc
-	makedepends = sdl2
-	makedepends = libsoup
-	makedepends = libnotify
-	makedepends = gstreamer
-	makedepends = gst-plugins-bad-libs
-	makedepends = ffmpeg
-	makedepends = jack
-	makedepends = nasm
 	makedepends = conan
+	makedepends = ffmpeg
+	makedepends = gcc
+	makedepends = git
+	makedepends = gst-plugins-bad-libs
+	makedepends = gstreamer
+	makedepends = jack
+	makedepends = libnotify
+	makedepends = libsoup
+	makedepends = nasm
+	makedepends = sdl2
 	depends = alsa-lib
-	depends = libx11
-	depends = gtk3
 	depends = expat
+	depends = flac
+	depends = gtk3
 	depends = libid3tag
+	depends = libmad
 	depends = libogg
 	depends = libsndfile
+	depends = libsoxr
 	depends = libvorbis
+	depends = libx11
 	depends = lilv
 	depends = lv2
+	depends = portaudio
 	depends = portsmf
+	depends = soundtouch
 	depends = suil
-	depends = libmad
 	depends = twolame
 	depends = vamp-plugin-sdk
-	depends = libsoxr
-	depends = soundtouch
+	depends = zlib
 	optdepends = ffmpeg: additional import/export capabilities
 	provides = audacity
 	conflicts = audacity