C#: Replace libnethost dependency to find hostfxr

[neikeq]

We want to replace libnethost as it gives us issues with some compilers.
Our implementation tries to mimic libnethost's hostfxr_resolver search logic. We try to use the same function names for easier comparing in case we need to update this in the future.

[akien-mga]

Gave this a try on the official buildsystem, it seems to fail building for Linux at least with our custom Linux toolchain: https://downloads.tuxfamily.org/godotengine/toolchains/

In file included from /root/x86_64-godot-linux-gnu_sdk-buildroot/x86_64-godot-linux-gnu/sysroot/usr/include/sys/types.h:222,
                 from /root/x86_64-godot-linux-gnu_sdk-buildroot/x86_64-godot-linux-gnu/sysroot/usr/include/stdlib.h:314,
                 from /root/x86_64-godot-linux-gnu_sdk-buildroot/x86_64-godot-linux-gnu/include/c++/10.2.0/cstdlib:75,
                 from /root/x86_64-godot-linux-gnu_sdk-buildroot/x86_64-godot-linux-gnu/include/c++/10.2.0/ext/string_conversions.h:41,
                 from /root/x86_64-godot-linux-gnu_sdk-buildroot/x86_64-godot-linux-gnu/include/c++/10.2.0/bits/basic_string.h:6535,
                 from /root/x86_64-godot-linux-gnu_sdk-buildroot/x86_64-godot-linux-gnu/include/c++/10.2.0/string:55,
                 from /root/x86_64-godot-linux-gnu_sdk-buildroot/x86_64-godot-linux-gnu/include/c++/10.2.0/stdexcept:39,
                 from /root/x86_64-godot-linux-gnu_sdk-buildroot/x86_64-godot-linux-gnu/include/c++/10.2.0/system_error:41,
                 from /root/x86_64-godot-linux-gnu_sdk-buildroot/x86_64-godot-linux-gnu/include/c++/10.2.0/mutex:42,
                 from ./core/os/mutex.h:39,
                 from ./core/os/thread_safe.h:34,
                 from ./core/object/message_queue.h:35,
                 from ./core/object/object.h:35,
                 from ./core/variant/binder_common.h:35,
                 from ./core/object/method_bind.h:34,
                 from ./core/object/class_db.h:34,
                 from ./core/object/ref_counted.h:34,
                 from ./modules/regex/regex.h:34,
                 from modules/mono/editor/semver.h:35,
                 from modules/mono/editor/semver.cpp:31:
modules/mono/editor/semver.h: In constructor 'godotsharp::SemVer::SemVer(int, int, int, const String&, const String&)':
modules/mono/editor/semver.h:80:4: error: class 'godotsharp::SemVer' does not have any field named 'gnu_dev_major'
   80 |    major(p_major),
      |    ^~~~~
modules/mono/editor/semver.h:81:4: error: class 'godotsharp::SemVer' does not have any field named 'gnu_dev_minor'
   81 |    minor(p_minor),
      |    ^~~~~

[neikeq]

That seems to be some weird glibc issue. One of the included headers defines major and minor macros that expand to that.

[akien-mga]

We currently use glibc 2.19 for the official toolchain to maximize compatibility: https://github.com/godotengine/buildroot/#godot-buildroot

Even by old glibc standards it's pretty old so we'll likely bump it to something a couple of years newer eventually, but that's pending on doing a general update pass of the buildroot config.

major is indeed defined here:

$ rg "define major"
x86_64-godot-linux-gnu/sysroot/usr/include/sys/sysmacros.h
61:#define major(dev) gnu_dev_major (dev)

That being said on my Mageia 9 machine with glibc 2.36 I also have the same:

/usr/include/sys/sysmacros.h
60:#define major(dev) gnu_dev_major (dev)

No idea why sys/sysmacros.h ends un included here and why it defines such a common name. I guess potential workarounds are to use a different name or #undef major before using it.

[neikeq]

Yes, I'll just undefine it. Found one such instance here:

godot/thirdparty/vulkan/include/vulkan/vulkan.hpp

Lines 132 to 140 in 86dd3f3

	// <tuple> includes <sys/sysmacros.h> through some other header
	// this results in major(x) being resolved to gnu_dev_major(x)
	// which is an expression in a constructor initializer list.
	#if defined( major )
	# undef major
	#endif
	#if defined( minor )
	# undef minor
	#endif

[akien-mga]

Thanks!