aliBuild: O2 does not need rebuild

I reinstalled o2 on cs8. Everything works fine. But if I modify some code, e.g. cxx file and try to recompile:
aliBuild build O2 --defaults o2
it does not compile:
Development package O2 does not need rebuild
Any ideas ?

After adding module ninja:
alienv enter O2/latest-ctpdev-o2 ninja/latest-ctpdev-o2
I can compile by
ninja install

So what is the standard way for development code ?

How did you create the development package? Is it named O2 and at the same level as alidist?

I was following github procedure I guess.
My dir structure is following:
[rl@ctpo2cs8 sw]$ ls
alidist BUILD dpl-config.json INSTALLROOT MIRROR MODULES O2 slc8_x86-64 SOURCES SPECS TARS
[rl@ctpo2cs8 sw]$ pwd
/home/rl/alice/sw
[rl@ctpo2cs8 sw]$ echo $ALIBUILD_WORK_DIR/
/home/rl/alice/sw/
[rl@ctpo2cs8 sw]$

Mmm… I am afraid you were not. You should have:

/home/rl/alice/O2
/home/rl/alice/alidist
/home/rl/alice/sw

and you should execute alibuild from /home/rl/alice.

Giulio, it seems I screw it, sorry. Thanks.

I fixed it reinstalling everything:
[rl@ctpo2cs8 alice]$ ls -l
total 16
drwxrwxr-x. 5 rl rl 8192 Jan 7 10:22 alidist
drwxrwxr-x. 28 rl rl 4096 Jan 7 11:30 O2
drwxrwxr-x. 11 rl rl 137 Jan 7 14:00 sw
[rl@ctpo2cs8 alice]$

But when I go to environment :
[O2/latest-ctpdev-o2] ~/alice/sw/BUILD/O2-latest-ctpdev/O2 $> ninja
bash: ninja: command not found
[O2/latest-ctpdev-o2] ~/alice/sw/BUILD/O2-latest-ctpdev/O2 $>
I can not still see ninja ?

Ninja is not part of the runtime environment you need to load it by hand (maybe we should change that, I will discuss it for the next meeting).