added a new build module for statically linked toybox (toybox_static)

In order to enable modprobe in recovery mode (for Treble), this change
add a target for building statically linked toybox (toybox_static). The
binary is installed in /sbin of root file system along with symbolic
link to it for 'modprobe'.

Bug: 35633646
Test: Build and tested it works in recovery
Change-Id: I589c4a248e135c6c0e25aadd063717c87369ef40
1 file changed