ffmpeg package: add aom support (#11210)

* Add Aom package
* Add aom variant to ffmpeg package which controls whether to build
  with the Aom dependency

var/spack/repos/builtin/packages/aom/package.py

@@ -0,0 +1,19 @@
+# Copyright 2013-2019 Trinity College Dublin and other Spack Project
+# Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+from spack import *
+
+
+class Aom(CMakePackage):
+    """Alliance for Open Media AOM AV1 Codec Library"""
+    homepage = "https://aomedia.googlesource.com/aom"
+    git      = "https://aomedia.googlesource.com/aom"
+    version('v1.0.0-errata1', commit='29d8ce4836630df5cc7ab58f1afc4836765fc212')
+    depends_on('yasm')
+
+    def cmake_args(self):
+        args = []
+        args.append('-DBUILD_SHARED_LIBS=ON')
+        return args

var/spack/repos/builtin/packages/ffmpeg/package.py

@@ -11,15 +11,20 @@ class Ffmpeg(AutotoolsPackage):
     convert and stream audio and video."""
 
     homepage = "https://ffmpeg.org"
-    url      = "http://ffmpeg.org/releases/ffmpeg-3.2.4.tar.bz2"
+    url      = "http://ffmpeg.org/releases/ffmpeg-4.1.1.tar.bz2"
 
+    version('4.1.1',   '4a64e3cb3915a3bf71b8b60795904800')
     version('4.1',   'b684fb43244a5c4caae652af9022ed5d85ce15210835bce054a33fb26033a1a5')
     version('3.2.4', 'd3ebaacfa36c6e8145373785824265b4')
 
     variant('shared', default=True,
             description='build shared libraries')
 
+    variant('aom', default=False,
+            description='build Alliance for Open Media libraries')
+
     depends_on('yasm@1.2.0:')
+    depends_on('aom', when='+aom')
 
     def configure_args(self):
         spec = self.spec
@@ -28,4 +33,9 @@ def configure_args(self):
         if '+shared' in spec:
             config_args.append('--enable-shared')
 
+        if '+aom' in spec:
+            config_args.append('--enable-libaom')
+        else:
+            config_args.append('--disable-libaom')
+
         return config_args