libaom: use git stub instead of patching changelog

It probably needs less maintenance.

pkgs/development/libraries/libaom/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchgit, yasm, perl, cmake, pkgconfig, python3Packages, writeText }:
+{ stdenv, fetchgit, yasm, perl, cmake, pkgconfig, python3, writeText }:
 
 stdenv.mkDerivation rec {
   name = "libaom-${version}";
@@ -10,33 +10,22 @@ stdenv.mkDerivation rec {
     sha256 = "07h2vhdiq7c3fqaz44rl4vja3dgryi6n7kwbwbj1rh485ski4j82";
   };
 
-  buildInputs = [ perl yasm ];
+  nativeBuildInputs = [
-  nativeBuildInputs = [ cmake pkgconfig python3Packages.python ];
+    yasm perl cmake pkgconfig python3
+  ];
 
-  cmakeFlags = [ "-DBUILD_SHARED_LIBS=ON" ];
+  cmakeFlags = [
+    "-DBUILD_SHARED_LIBS=ON"
+  ];
 
-  # * libaom tries to detect what version it is
+  preConfigure = ''
-  #   * I couldn't get it to grab this from git info,
+    # build uses `git describe` to set the build version
-  #     (which needs at least leaveDotGit=true)
+    cat > $NIX_BUILD_TOP/git << "EOF"
-  #   * it uses a perl script to parse from CHANGELOG,
+    #!${stdenv.shell}
-  #     but 1.0.0 doesn't contain an entry for itself :(
+    echo v${version}
-  # * Upstream patch that adds the entry also nukes all of
+    EOF
-  #   the versions before a project change (open-sourcing?)
+    chmod +x $NIX_BUILD_TOP/git
-  #   and as a result is 34K which is way too big just to fix this!
+    export PATH=$NIX_BUILD_TOP:$PATH
-  #   * A stable URL to fetch this from works, but...
-  # * Upon inspection the resulting CHANGELOG is shorter
-  #   than this comment, so while yes this is a bit gross
-  #   adding these 4 lines here does the job without
-  #   a huge patch in spirit of preferring upstream's fix
-  #   instead of `sed -i 's/v0\.1\.0/v1.0.0/g' aom.pc` or so.
-  postPatch = let actual_changelog = writeText "CHANGELOG" ''
-    2018-06-28 v1.0.0
-      AOMedia Codec Workgroup Approved version 1.0
-
-    2016-04-07 v0.1.0 "AOMedia Codec 1"
-      This release is the first Alliance for Open Media codec.
-  ''; in ''
-   cp ${actual_changelog} CHANGELOG
   '';
 
   meta = with stdenv.lib; {