Use scons target and dependency system instead of ad-hoc options.
Now is simply a matter of naming what to build. For example:
scons libgl-xlib
scons libgl-gdi
scons graw-progs
scons llvmpipe
and so on. And there is also the possibility of scepcified subdirs, e.g.
scons src/gallium/drivers
If nothing is specified then everything will be build.
There might be some rough corners over the next days. Please bare with me.
Also added calls to the create function in target helpers and in
tr_drm.c the latter being a hack and should be replaced with the
wrap screen target helper. But at least this way we don't regress.
These are our reference software rasterizers. They can build everywhere
and are a precious debugging tool.
Making them always present immensily simplifies the scons logic.
If people want to avoid building it is still possible to pass
direcotries and target names to scons to narrow the build.
Now that draw depends on llvm it is very difficult to correctly handle
broken llvm installations. Either the user requests LLVM and it needs to
supply a working installation. Or it doesn't, and it gets no LLVM
accelerate pipe drivers.
Currently there are still at least two functions bundled up inside the
winsys concept:
a) that of a backend resource manager, sometimes capable of performing
present() operations,
b) the initialization code/routine for the whole driver stack.
The inclusion of (b) makes it difficult to share implementations of
(a) between different drivers. For instance, a clean xlib winsys
could be of use for software-rasterized VG, GLES, EGL, etc, stacks.
But that is only true as long as there is no dependency from the
winsys to higher level code, as would be the case when we include (b)
in this component.
This change creates a new gallium/targets subtree, specifically for
implementing the glue needed to build individual driver stacks, and
moves that code out of a single example winsys, namely xlib.
Other drivers continue to build unchanged, but hopefully can migrate
to this structure over time.
