Add a direct build dependency on linux_base instead of relying on devtools
to pull it in. This guarantees that the version constraint set in
Mk/Uses/linux.mk is taken into account.

Compile with --sysroot=${LINUXBASE} such that gcc doesn't pick up headers
from /usr.

Build the 32 bit library on amd64 with -m32 such that it's actually a 32 bit
library. This must have become broken long time ago when 64 bit linux
support was added and the compiler became 64 bit. [1]

PR: 249516
Reported by: Alex S <iwtcex@gmail.com> [1]