When building with mingw32-make, it prefers executing commands
through "sh.exe" if it is available.
When busybox sh.exe executes "ar", it prefers executing its own
internal tool over a potential external tool found in $PATH.
(This can be avoided by setting 'export BB_OVERRIDE_APPLETS="ar"',
but as this build of busybox is expected to be used with llvm-mingw,
disable the built-in "ar" tool outright.)
Martin Storsjö