ipmiutil: needs dynamic library support

ipmiutil builds libipmiutil.so unconditionally.

Fixes:
http://autobuild.buildroot.net/results/e31/e31d94847cad9216aad839c2fbb312e9ea0ae75e/
http://autobuild.buildroot.net/results/5f3/5f3f32473186e6fa3a165b263f682047af8e291e/



Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>