std.Build.LazyPath: add getPath3; deprecate getPath2 and getPath

The goal is to move towards using `std.Build.Cache.Path` instead of
absolute path names.

This was helpful for implementing file watching integration to
the InstallDir Step
26bdc836d2Andrew Kelley committed on 7/12/2024, 7:14:08 AMparent0994e22
1 file changedLine totals unavailable