Fix compilation for deprecated API on macOS Mojave preview

[maryamariyan]

Relates to: #30599

cc: @danmosemsft @bartonjs

[danmoseley]

This is only a temporary workaround... Is it possible to add a comment in this file with the issue you are using to track checking in your correct fix?

[danmoseley]

I assume that issue is not #30599 since this issue is currently set to close it

[maryamariyan]

@danmosemsft changing from "fixes" to "related to", so closing the PR won't close the issue.

[bartonjs]

Are there multiple projects that need this? If it's just the crypto shim then I'd expect this to be in that specific file.

[filipnavara]

Should be moved to src/Native/Unix/System.Security.Cryptography.Native.Apple/CMakeLists.txt

[ghost]

Currently there is only one place that defines these: this file. To be consistent with the current norm, should it be kept here?
When the second project will require it, nobody will remember that it is also in a project-specific file to move at global location.

---

The second one-off approach is in the .c file, such as:

corefx/src/Native/Unix/System.Net.Security.Native/pal_gssapi.h

Lines 47 to 54 in 44e5bda

	#pragma clang diagnostic push
	#pragma clang diagnostic ignored "-Wpadded"
	typedef struct
	{
	uint64_t length;
	uint8_t* data;
	} PAL_GssBuffer;
	#pragma clang diagnostic pop

and

corefx/src/Native/Unix/System.Native/pal_networking.c

Lines 844 to 850 in 44e5bda

	#pragma clang diagnostic push
	#pragma clang diagnostic ignored "-Wsign-compare"
	#endif
	return CMSG_NXTHDR(mhdr, cmsg);
	#ifndef __GLIBC__
	#pragma clang diagnostic pop
	#endif

[bartonjs]

Currently there is only one place that defines these: this file. To be consistent with the current norm, should it be kept here?

I believe that the intention is that it will be deleted fairly soon, and if everything else is compiling without that flag then there won't be a second place.

[bartonjs]

@danmosemsft This line we'll want to send to release/2.1 at whatever rate we say we support Mojave