[R] Enable R build process to find locally built C++ library on Windows

[asfimport]

Currently, configure.win and tools/winlibs.R have two ways of finding the Arrow C++ library:

1. If RWINLIB_LOCAL is set, it gets it from that zip file

2. If not, it downloads it

   Enable and document a third option for the case when the C++ library has been built locally. This will enable R package developers using Windows machines to make changes to code in the C++ library, build and install it, and then build the R package using it.

Reporter: Will Jones / @wjones127
Assignee: Will Jones / @wjones127

PRs and other links:

• GitHub Pull Request #11644

_{Note: This issue was originally created as ARROW-11938. Please see the migration documentation for further details.}

[asfimport]

Ian Cook / @ianmcook:
See the find_local_source function in r/inst/linuxlibs.R which handles this situation on non-Windows systems, but note that that attempts to build the C++ library, not just find it if it’s already built, and we probably do not want to attempt to script C++ library build on users’ Windows environments.

[asfimport]

Jonathan Keane / @jonkeane:
Issue resolved by pull request 11644
#11644