Nirbheek Chauhan authored Nov 22, 2018 and Nirbheek Chauhan committed Nov 23, 2018

Sometimes we need to access the currently-used visual studio version
from inside recipes to set configuration flags. F.ex., libvpx.

Nirbheek Chauhan authored Nov 11, 2018 and Sebastian Dröge committed Nov 11, 2018

Closes #85

Instead of computing the vcvarsall at the module level, add a function
for it and use that. This also allows us to target a specific version
of Visual Studio (2015/2017/etc).

We were accidentally using the full value of PATH set in the VS command
prompt as the PATH value that contains Visual Studio paths. Only
a subset of that value contains Visual Studio paths.

As a part of this, now the rest of the code prepends PATH fetched from
VS to the existing PATH value and uses the other env vars as-is by
overwriting.

The VS 2017 batch files print message to stdout that mess up the
environment extraction. Try to silence them, and ignore whatever else
it decides to print unconditionally.

Unless the 'visualstudio' variant is disabled in the config by enabling
the `novisualstudio` variant, recipes that use Meson will be built
using Visual Studio.

Cerbero will attempt to find either Visual Studio 2015 or Visual Studio
2017 and set the correct environment to use the MSVC toolchain. This
is done once at startup, and then used by each recipe at build time.

To get this environment in shell form, use the `win32-msvc-shell.cbc`
and `win64-msvc-shell.cbc` config files.

https://bugzilla.gnome.org/show_bug.cgi?id=796641