godot: stop build process from looking in global directories

pkgs/development/tools/godot/default.nix

@@ -23,10 +23,13 @@ in stdenv.mkDerivation rec {
   buildInputs = [
     gcc5 scons libX11 libXcursor libXinerama libXrandr libXrender
     libXi libXext libXfixes freetype openssl alsaLib libpulseaudio
-    libGLU zlib
+    libGLU zlib yasm
   ];
 
-  patches = [ ./pkg_config_additions.patch ];
+  patches = [
+    ./pkg_config_additions.patch
+    ./dont_clobber_environment.patch
+  ];
 
   enableParallelBuilding = true;
 

pkgs/development/tools/godot/dont_clobber_environment.patch

@@ -0,0 +1,16 @@
++++ build/SConstruct
+@@ -69,10 +69,10 @@
+         custom_tools = ['mingw']
+ 
+ env_base = Environment(tools=custom_tools)
+-if 'TERM' in os.environ:
+-    env_base['ENV']['TERM'] = os.environ['TERM']
+-env_base.AppendENVPath('PATH', os.getenv('PATH'))
+-env_base.AppendENVPath('PKG_CONFIG_PATH', os.getenv('PKG_CONFIG_PATH'))
++for k in ("TERM", "PATH", "PKG_CONFIG_PATH"):
++    if (k in os.environ):
++        env_base["ENV"][k] = os.environ[k]
++
+ env_base.global_defaults = global_defaults
+ env_base.android_maven_repos = []
+ env_base.android_flat_dirs = []