Update ffmpeg-libfdk_aac to 4.2.1

ffmpeg/libfdk_aac/PKGBUILD

@@ -9,8 +9,8 @@
 
 _name=ffmpeg
 pkgname=ffmpeg-libfdk_aac
-pkgver=4.2
-pkgrel=2
+pkgver=4.2.1
+pkgrel=1
 epoch=1
 pkgdesc='Complete solution to record, convert and stream audio and video (with libfdk-aac support)'
 arch=('x86_64')
@@ -88,14 +88,20 @@ provides=(
   "ffmpeg=$pkgver"
 )
 conflicts=("$_name")
-source=("git+https://git.ffmpeg.org/ffmpeg.git#tag=n${pkgver}")
-sha256sums=('SKIP')
+source=(git+https://git.ffmpeg.org/ffmpeg.git#tag=cbb3c9497549f8856d8cd37ac63af1406a784e58)
+sha256sums=(SKIP)
+
+pkgver() {
+  cd ffmpeg
+
+  git describe --tags | sed 's/^n//'
+}
 
 build() {
   cd $_name
 
   ./configure \
-    --prefix='/usr' \
+    --prefix=/usr \
     --disable-debug \
     --disable-static \
     --disable-stripping \