x265: fix ARM cross compilation

pkgs/development/libraries/x265/default.nix

@@ -25,6 +25,8 @@
 let
   mkFlag = optSet: flag: if optSet then "-D${flag}=ON" else "-D${flag}=OFF";
 
+  isCross = stdenv.buildPlatform != stdenv.hostPlatform;
+
   cmakeCommonFlags = [
     "-Wno-dev"
     (mkFlag custatsSupport "DETAILED_CU_STATS")
@@ -81,6 +83,8 @@ stdenv.mkDerivation rec {
       url = "https://gitweb.gentoo.org/repo/gentoo.git/plain/media-libs/x265/files/test-ns.patch?id=1d1de341e1404a46b15ae3e84bc400d474cf1a2c";
       sha256 = "0zg3g53l07yh7ar5c241x50y5zp7g8nh8rh63ad4bdpchpc2f52d";
     })
+    # Fix detection of NEON (and armv6 build) :
+    ./fix-neon-detection.patch
   ];
 
   postPatch = ''
@@ -107,7 +111,7 @@ stdenv.mkDerivation rec {
     "-DENABLE_SHARED=${if stdenv.hostPlatform.isStatic then "OFF" else "ON"}"
     "-DHIGH_BIT_DEPTH=OFF"
     "-DENABLE_HDR10_PLUS=ON"
-  ] ++ [
+    (mkFlag (isCross && stdenv.hostPlatform.isAarch) "CROSS_COMPILE_ARM")
     (mkFlag cliSupport "ENABLE_CLI")
     (mkFlag unittestsSupport "ENABLE_TESTS")
   ] ++ lib.optionals (multibitdepthSupport) [

pkgs/development/libraries/x265/fix-neon-detection.patch

@@ -0,0 +1,28 @@
+commit 72489cd0a1c229258abe4f20e4fdfd414dfa88da
+Author: rnhmjoj <rnhmjoj@inventati.org>
+Date:   Sun Oct 2 00:15:24 2022 +0200
+
+    Fix NEON detection
+
+diff --git a/cmake/FindNeon.cmake b/cmake/FindNeon.cmake
+index 0062449..9c436d9 100644
+--- a/cmake/FindNeon.cmake
++++ b/cmake/FindNeon.cmake
+@@ -1,10 +1,11 @@
+ include(FindPackageHandleStandardArgs)
+ 
+ # Check the version of neon supported by the ARM CPU
+-execute_process(COMMAND cat /proc/cpuinfo | grep Features | grep neon
+-                OUTPUT_VARIABLE neon_version
+-                ERROR_QUIET
+-                OUTPUT_STRIP_TRAILING_WHITESPACE)
+-if(neon_version)
+-    set(CPU_HAS_NEON 1)
++message(STATUS "Detecting NEON support")
++execute_process(COMMAND sed -n "/Features.* neon/q 1" /proc/cpuinfo
++                RESULT_VARIABLE CPU_HAS_NEON)
++if(CPU_HAS_NEON)
++    message(STATUS "Detecting NEON support - supported")
++else()
++    message(STATUS "Detecting NEON support - not supported" )
+ endif()