Explicitly add msys2 as path dependency of libadwaita

In `libadwaita` 1.4.0, the `demo/data/meson.build` was changed to
require `sh` [1].
However, this is causing a `Program 'sh' not found` error in `gvsbuild`
because `sh` isn't on the `$PATH` by default.

Resolve this by adding MSYS2's `sh` to the `$PATH`.

Fixes #1133

[1] https://gitlab.gnome.org/GNOME/libadwaita/-/commit/daeb5a6b78a8530b78f7d495deb02f4e97f26e7b

gvsbuild/projects/libadwaita.py

@@ -32,6 +32,7 @@ def __init__(self):
  dependencies=[
  "ninja",
  "meson",
+ "msys2",
  "pkgconf",
  "glib",
  "gtk4",
@@ -51,5 +52,6 @@ def __init__(self):
  self.add_param("-Dvapi=false")
 
  def build(self, **kwargs):
- Meson.build(self)
+ msys_path = Project.get_tool_path("msys2")
+ Meson.build(self, add_path=msys_path)
  self.install(r".\COPYING share\doc\libadwaita")