Feature request: use `pkgbuild` to build the package

[Yunuuuu]

Related to r-lib/pkgbuild#59

pkgbuild provides a mechanism to avoid copying large files during the build process by using symlinks or similar strategies.

However, when using pak::pak("."), it appears that the entire package directory is copied, which makes the process significantly slower for packages containing large files. In contrast, building the package first with pkgbuild::build() and then installing the tarball using pak::pak("local::../my_pkg.tar.gz") is much faster:

pkgbuild::build()
pak::pak("local::../rsahmi_0.0.2.9000.tar.gz")