Previously the partial UCRT path obtained from `ucrtPaths` would always start with `\`.
Combined with the behavior of Path.Combine(p1,p2) to always return p2 when it is absolute, we'd always end up with an incomplete partial path.
Errors:
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\xtr1common(227,22): error: use of undeclared identifier 'char16_t'
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\xtr1common(233,22): error: use of undeclared identifier 'char32_t'
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\xstddef(408,14):error: use of undeclared identifier 'char16_t'
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\xstddef(414,14):error: use of undeclared identifier 'char32_t'
C:\Program Files (x86)\Windows Kits\8.1\include\um\winnt.h(938,2): error: Must define a target architecture.
C:\Program Files (x86)\Windows Kits\8.1\include\um\oaidl.h(473,31): error: cannot combine with previous 'type-name' declaration specifier