onnxruntime: fix cross-compilation

Three things break the cross build:

- doCheck was true, so CMake tried to build tests and fetch GTest.
  FETCHCONTENT_FULLY_DISCONNECTED blocks the download, and the tests
  can't run on the build machine anyway. Disable doCheck when
  host != build.
- pythonSupport defaulted to true, but FindPython runs the
  build-platform Python, which can't find target-platform NumPy
  headers. Default to false when not canExecute.
- protobuf was only in nativeBuildInputs (for protoc), so the linker
  found the build-platform libprotobuf-lite.so. Add it to buildInputs
  too.

Resolves NixOS#462791

pkgs/by-name/on/onnxruntime/package.nix

@@ -21,7 +21,7 @@
   protobuf,
   microsoft-gsl,
   darwinMinVersionHook,
-  pythonSupport ? true,
+  pythonSupport ? (stdenv.buildPlatform.canExecute stdenv.hostPlatform),
   cudaSupport ? config.cudaSupport,
   ncclSupport ? cudaSupport && cudaPackages.nccl.meta.available,
   rocmSupport ? config.rocmSupport,
@@ -165,6 +165,7 @@ effectiveStdenv.mkDerivation (finalAttrs: {
     libpng
     nlohmann_json
     microsoft-gsl
+    protobuf
     zlib
   ]
   ++ lib.optionals (lib.meta.availableOn effectiveStdenv.hostPlatform cpuinfo) [
@@ -313,6 +314,8 @@ effectiveStdenv.mkDerivation (finalAttrs: {
     !(
       cudaSupport
       || rocmSupport
+      # cross-compiled test binaries can't execute on the build platform
+      || (effectiveStdenv.hostPlatform != effectiveStdenv.buildPlatform)
       || builtins.elem effectiveStdenv.buildPlatform.system [
         # aarch64-linux fails cpuinfo test, because /sys/devices/system/cpu/ does not exist in the sandbox
         "aarch64-linux"