config.h is generated in build/, that's "../" at compile time.

For the sake of completeness, here's the waf error:

[122/163] cxx: common/Jackdmp.cpp -> build/common/Jackdmp.cpp.1.o
In file included from ../common/Jackdmp.cpp:35:0:
../common/JackConstants.h:24:20: fatal error: config.h: No such file or directory
compilation terminated.
Waf: Leaving directory `/home/adi/jack2/build'
Build failed
 -> task in 'jackd' failed (exit status 1):
        {task 39469904: cxx Jackdmp.cpp -> Jackdmp.cpp.1.o}
['/usr/bin/g++', '-Wall', '-I/home/adi/jack2/build/linux', '-I/home/adi/jack2/linux', '-I/home/adi/jack2/build/posix', '-I/home/adi/jack2/posix', '-I/home/adi/jack2/build/common/jack', '-I/home/adi/jack2/common/jack', '-I/home/adi/jack2/build/common', '-I/home/adi/jack2/common', '-I/home/adi/jack2/build/dbus', '-I/home/adi/jack2/dbus', '-DHAVE_CONFIG_H', '-DSERVER_SIDE', '../common/Jackdmp.cpp', '-c', '-o', 'common/Jackdmp.cpp.1.o']