Improve CMake detection on Windows when not in PATH (#16328)

Improve CMake detection on Windows when not in PATH (#16328)

Port dotnet/corert#5372

curl https://github.com/dotnet/corert/commit/b723f90c611a2c79a0921f95c7299ebb7325eb59.patch | git am -p 3 --directory='src/pal/tools/' --reject

In CMake v10.2, the key `hklm:\SOFTWARE\Kitware` returns:

```powershell
    Hive: HKEY_LOCAL_MACHINE\SOFTWARE\Kitware

Name                           Property
----                           --------
CMake                          InstallDir : C:\Program Files\CMake\
```

with no space after `CMake` and property name `InstallDir`,
instead of `'(default)'`.