Fix project default-build overriding the per-target default-build.

[grafikrobot]

No description provided.

[pdimov]

This fixes b2 build//dist-bin:

...patience...
...patience...
...found 3643 targets...
...updating 1 target...
common.copy C:\boost-git\develop\dist\bin\inspect.exe
..\..\bin.v2\tools\inspect\build\msvc-14.3\release\x86_64\link-static\threading-multi\inspect.exe
        1 file(s) copied.

...updated 1 target...

and b2 dist-bin, using the root target, works too:

...patience...
...patience...
...found 3643 targets...
...updating 1 target...
common.copy C:\boost-git\develop\dist\bin\inspect.exe
..\..\bin.v2\tools\inspect\build\msvc-14.3\release\x86_64\link-static\threading-multi\inspect.exe
        1 file(s) copied.

...updated 1 target...

However, b2 dist still installs debug :-)

...patience...
...patience...
...found 3643 targets...
...updating 1 target...
common.copy C:\boost-git\develop\dist\bin\inspect.exe
..\..\bin.v2\tools\inspect\build\msvc-14.3\debug\x86_64\link-static\threading-multi\inspect.exe
        1 file(s) copied.

B2 wonders never cease :-)

The default-build parameter of the individual targets doesn't seem very useful. Looks like it's only (somewhat) reliable if put on the projects.

[grafikrobot]

Nah, it's the same problem. B2 picks the first default encountered while determining the target build request. And depending on where the default is set you get difference results. Here's the equivalent change tot he top-level as the one from before int he build dir.. #22