pkgbuild 1.4.8

• New Config/build/never-clean DESCRIPTION option to avoid adding
  --preclean to R CMD INSTALL (e.g., when header files have changed)
  (@krlmlr, #204).

• has_rtools() & co. now work correctly on aarch64 Windows, when
  RTOOLS45_AARCH64_HOME is not set (@remlapmot, #203).

• pkg_build() and pkgbuild_process now work corrently when building
  binary packages from non-standard file names (#208).