add 'file' as a build-base dependency
When building packages for mips64, various packages refuse to build
shared libraries because the configure script depends on /usr/bin/file
to detect which ABI to use [1]. However, this tool is not provided
as
part of the build-base and is not explicitly listed as a
make-dependency
for each of the affected packages.
Other projects have ran into this issue before and have made this
utility a requirement [2].
[1]
http://git.savannah.gnu.org/cgit/libtool.git/commit/?id=5f7f7d9615bf650cf99d581a33b3e18357f79951
[2]
https://git.buildroot.net/buildroot/commit/support/dependencies?id=e09e1873a1b5d33fa2e9787b964abb575bc335a4
(from redmine: issue id 8406, created on 2018-01-20, closed on 2018-06-25)