Mirror changes from dotnet/coreclr

[Dotnet-GitSync-Bot]

This PR contains mirrored changes from dotnet/coreclr

Please REBASE this PR when merging

cc @stephentoub

[stephentoub]

@jkotas, are these WebAssembly legs known to fail, or did I likely cause the failures?

[jkotas]

They fail because of we are calling GetUnixName very early during the startup here now:

15:25:50 abort@http://localhost:6931/HelloWasm.js:7085:44
15:25:50 _SystemNative_GetUnixName@http://localhost:6931/HelloWasm.js:2022:69
15:25:50 _S_P_CoreLib_Interop_Sys__GetUnixNamePrivate@http://localhost:6931/HelloWasm.js:1542080:1
15:25:50 _S_P_CoreLib_Interop_Sys__GetUnixName@http://localhost:6931/HelloWasm.js:1373820:1
15:25:50 _S_P_CoreLib_System_Environment___cctor@http://localhost:6931/HelloWasm.js:1373394:1
15:25:50 _S_P_CoreLib_System_Runtime_CompilerServices_ClassConstructorRunner__Call@http://localhost:6931/HelloWasm.js:1175463:1
15:25:50 _S_P_CoreLib_System_Runtime_CompilerServices_ClassConstructorRunner__EnsureClassConstructorRun@http://localhost:6931/HelloWasm.js:1146612:1
15:25:50 _S_P_CoreLib_System_Environment__SetCommandLineArgs@http://localhost:6931/HelloWasm.js:1164711:1

Calling GetUnixName on startup path is not nice. GetUnixName call is not required in CoreLib to figure out where we are on OSX. CoreLib is compiled OS-specific and we do have PLATFORM_OSX defined for Mac. We should use this define here.

(It is fine to append commits that modify shared partition to this PR. They will get mirrored once the PR is merged.)

[stephentoub]

we do have PLATFORM_OSX defined for Mac. We should use this define here.

Ok. Thanks.