Add missing Makefile rule for generating the auto_check_header_qbconfig.c file

Resolves issue #158

Addressing:
make[2]: Entering directory `/home/dkopecek/Projects/github/usbguard/src/ThirdParty/libqb/_build/tests'
...

GEN      auto_check_header_qbarray.c
CC       auto_check_header_qbarray.o
CCLD     auto_check_header_qbarray

make[2]: * No rule to make target auto_check_header_qbconfig.c', needed by auto_check_header_qbconfig.o'. Stop.
make[2]: Leaving directory `/home/dkopecek/Projects/github/usbguard/src/ThirdParty/libqb/_build/tests'
make[1]: * [all-recursive] Error 1
make[1]: Leaving directory `/home/dkopecek/Projects/github/usbguard/src/ThirdParty/libqb/_build'
make: *** [all] Error 2