You receive this bug because this package installs '.a' file which should be handled by static-libs IUSE. Please also punt the '.la' file if they are not needed. From 'qlist -e ${package}': /usr/lib64/libnl.so /usr/lib64/libnl.a /usr/lib64/libnl.so.1.1.3 /usr/lib64/libnl.so.1
Most users of dev-libs/libnl:1.1 currently expect static library, so I've added IUSE=+static-libs. People filing bug reports against dependent packages (who have USE=-static-libs forced) shouldn't be surprised.
I've gone back on that one. I was perhaps confusing libnl with another package. IUSE=static-libs now, not +static-libs.