[llvm] RuntimeLibcalls: Add entries for __security_check_cookie (PR #151843)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Is this expected? 

Yes. Literal target checks should be minimized in favor of feature checks 

> Is the presents of security_check_cookie enough to imply isWindowsMSVCEnvironment (not withstanding the current definition of SecurityCheckCookieIfWinMSVC).

I don't know, but does it actually matter? If there's no reason to distinguish the OS when using these calls, it's just duplicating conditions 

> 
> Would is make sense to keep the `if isWindowsMSVCEnvironment` structure but then require/assert the RTLIB::LibcallImpl is supported?

I think that would be worse. I am trying to avoid the current spaghetti of subtlety different correlated conditions used in all of the libcall contexts. 

https://github.com/llvm/llvm-project/pull/151843