[clang] [profile] runtime counter relocation is needed on windows-msvc targets (PR #127858)

[Wael Yehia via cfe-commits]

w2yehia wrote:

> Can you summarize the high level use case which didn't work before, and in which way it used to fail before, which gets fixed by this change?

Continuous profiling (that is continuous profile syncing to disk) is an existing feature, which is OFF by default on most platforms. 
The feature [mmap's](https://github.com/llvm/llvm-project/blob/main/compiler-rt/lib/profile/InstrProfilingFile.c#L273) the profile file rather than writing it at program exit (the default non-continuous mode behavior). There are two implementations in `InstrProfilingFile.c`, [one](https://github.com/llvm/llvm-project/blob/main/compiler-rt/lib/profile/InstrProfilingFile.c#L160) that mmap's onto existing memory, and [another](https://github.com/llvm/llvm-project/blob/main/compiler-rt/lib/profile/InstrProfilingFile.c#L273) that mmap's without an address hint. The latter relies on a corresponding compiler action (added in [this](https://github.com/llvm/llvm-project/commit/d3db13af7e5c01632fbf28149a2d4f9c4841aeba) commit), which is enabled using `-mllvm -runtime-counter-relocation`. 

What I added, in a previous PR (#124353), was a clang option (-fprofile-continuous) to enable the feature and take care of the nuances of setting up the compiler and runtime: (1) override the profile file name by appending '%c' into it, and (2) pass `-runtime-counter-relocation` to the backend on certain platforms.
This PR added `T.isKnownWindowsMSVCEnvironment()` to the conditions under which the drivers passes `-runtime-counter-relocation` to the backend, and the question is whether this is sufficient for windows or more changes to the conditions are needed. 
Note if we miss a condition/configuration then it doesn't break the feature there, it just would [fail](https://github.com/llvm/llvm-project/blob/main/compiler-rt/lib/profile/InstrProfilingFile.c#L662) at runtime if you try enabling using this new clang option (-fprofile-continuous).

https://github.com/llvm/llvm-project/pull/127858