neatvnc: Disable the CPU acceleration by default

For Nixpkgs it seems best to disable the usage of CPU extensions by
default as older CPUs don't support them which will result in a crash at
runtime (SIGILL: Illegal instruction) [0].
The performance on my old test system was more than enough anyway
(usually ~10% CPU usage due to wayvnc).

[0]: https://github.com/any1/neatvnc/issues/21

pkgs/development/libraries/neatvnc/default.nix

@@ -1,6 +1,7 @@
 { stdenv, fetchFromGitHub, meson, pkg-config, ninja
 , pixman, libuv, gnutls, libdrm
 # libjpeg_turbo: Optional, for tight encoding (disabled because experimental)
+, enableCpuAcceleration ? false # Whether to use CPU extensions (e.g. AVX)
 }:
 
 stdenv.mkDerivation rec {
@@ -17,6 +18,8 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ meson pkg-config ninja ];
   buildInputs = [ pixman libuv gnutls libdrm ];
 
+  patches = stdenv.lib.optional (!enableCpuAcceleration) ./disable-cpu-acceleration.patch;
+
   meta = with stdenv.lib; {
     description = "A VNC server library";
     longDescription = ''

pkgs/development/libraries/neatvnc/disable-cpu-acceleration.patch

@@ -0,0 +1,17 @@
+diff --git a/meson.build b/meson.build
+index 31dd8b8..8761087 100644
+--- a/meson.build
++++ b/meson.build
+@@ -21,12 +21,6 @@ endif
+ 
+ cpu = host_machine.cpu_family()
+ 
+-if cpu == 'x86_64'
+-	c_args += '-mavx'
+-elif cpu == 'arm'
+-	c_args += '-mfpu=neon'
+-endif
+-
+ add_project_arguments(c_args, language: 'c')
+ 
+ cc = meson.get_compiler('c')