package/libqb: needs threads and dynamic library

package/libqb: needs threads and dynamic library

libqb fails to build without threads or dynamic library since the
addition of the package in commit
22864d570dd18d78a77dedab8fbcc5e0122c0acc

Also add ac_cv_prog_cc_c99=-std=gnu99 to fix build failure without wchar

Fixes:
 - http://autobuild.buildroot.org/results/21c1b5d29da4949f4582056ab4e2335ec225d8d6
 - http://autobuild.buildroot.org/results/aa4df6364cdf3c862be13b6b738595f420ec6105
 - http://autobuild.buildroot.org/results/376d316094238ba7097e8bdc51960ba38532683a

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>