abort early on missing dependency: gssapi.h for kerberos

when gssapi.h is missing,

in the middle of the builld phase, ninja throws

[13404/26121] CXX obj/net/net/http_auth_handler_factory.o

src/3rdparty/chromium/net/http/http_auth_gssapi_posix.h:25:10:

fatal error: gssapi.h: No such file or directory

expected: should be handled in configure phase

cmake config
-DQT_FEATURE_webengine_kerberos=ON
 
config summary
webengine_kerberos ..................... yes