libgee, libgda, zile: fix compiling with clang

-Wno-incompatible-function-pointer-types was removed from vala's setup
hook in b2d88d4. Without it, we're unable to compile libgee[1], libgda,
and zile on Darwin. The libgda and zile failures were masked by libgee
failing.

[1]: https://hydra.nixos.org/build/271035513

pkgs/applications/editors/zile/default.nix

@@ -39,6 +39,8 @@ stdenv.mkDerivation rec {
   # fiddle with the terminal.
   doCheck = false;
 
+  env.NIX_CFLAGS_COMPILE = lib.optionals stdenv.cc.isClang "-Wno-error=incompatible-function-pointer-types";
+
   # XXX: Work around cross-compilation-unfriendly `gl_FUNC_FSTATAT' macro.
   gl_cv_func_fstatat_zero_flag="yes";
 

pkgs/development/libraries/libgda/6.x.nix

@@ -85,6 +85,8 @@ stdenv.mkDerivation rec {
     postgresql
   ];
 
+  env.NIX_CFLAGS_COMPILE = lib.optionals stdenv.cc.isClang "-Wno-error=incompatible-function-pointer-types";
+
   postPatch = ''
     patchShebangs \
       providers/raw_spec.py \

pkgs/development/libraries/libgda/default.nix

@@ -82,6 +82,8 @@ stdenv.mkDerivation rec {
     "--enable-system-sqlite=${if stdenv.isDarwin then "no" else "yes"}"
   ];
 
+  env.NIX_CFLAGS_COMPILE = lib.optionals stdenv.cc.isClang "-Wno-error=incompatible-function-pointer-types";
+
   enableParallelBuilding = true;
 
   hardeningDisable = [ "format" ];

pkgs/development/libraries/libgee/default.nix

@@ -34,6 +34,7 @@ stdenv.mkDerivation (finalAttrs: {
   doCheck = true;
 
   env = {
+    NIX_CFLAGS_COMPILE = lib.optionalString stdenv.cc.isClang "-Wno-error=incompatible-function-pointer-types";
     PKG_CONFIG_GOBJECT_INTROSPECTION_1_0_GIRDIR = "${placeholder "dev"}/share/gir-1.0";
     PKG_CONFIG_GOBJECT_INTROSPECTION_1_0_TYPELIBDIR = "${placeholder "out"}/lib/girepository-1.0";
   };