System.Native: eng/native/tryrun.cmake host/target confusion

[lambdageek]

When doing an android-x86 build on an osx-arm64 machine, during ./build.sh --os android -arch x86, we end up here during the System.Native build

runtime/eng/native/tryrun.cmake

Line 90 in f83580d

message(FATAL_ERROR "Arch is ${TARGET_ARCH_NAME}. Only arm64 or x64 is supported for OSX cross build!")

This is the else case for

runtime/eng/native/tryrun.cmake

Lines 50 to 51 in f83580d

	if(DARWIN)
	if(TARGET_ARCH_NAME MATCHES "^(arm64|x64)$")

This seems wrong - DARWIN is the host machine (osx-arm64), arm64|x64 is checking the target architecture

[lambdageek]

Note that ./build.sh --os android -arch x86 will fail earlier, during the mono build, unless you include #89027

but after that it's an eng/native/tryrun.cmake problem

[lambdageek]

cc @directhex