kvm tools: Add build target for statically-linked binary

kvm tools: Add build target for statically-linked binary

This commit adds a target for 'lkvm-static' which is linked -static.

(This can be useful to construct kvmtool binaries for minimalist
auto-test host filesystems.)

Since extra features (SDL, AIO, VNC etc.) are auto-detected in the makefile
AND some features may only work when linked one way (but not both), the
feature detection now checks for both dynamic & static success.  Intermediate
objects build with correct flags (e.g. CONFIG_HAS_AIO) for the end target.

Signed-off-by: Matt Evans <matt@ozlabs.org>
Signed-off-by: Pekka Enberg <penberg@kernel.org>