More a reminder for myself, than a blog post...
If you want to backport a project from unstable based on the meson build system and your package uses debhelper to invoke the meson build process, then you need to modify the backported package's debian/control file slightly:
diff --git a/debian/control b/debian/control
index 43e24a2..d33e76b 100644
--- a/debian/control
+++ b/debian/control
@@ -14,7 +14,7 @@ Build-Depends: debhelper (>= 11~),
libmate-menu-dev (>= 1.16.0),
libmate-panel-applet-dev (>= 1.16.0),
libnotify-dev,
- meson,
+ meson (>= 0.40.0),
ninja-build,
pkg-config,
Standards-Version: 4.1.3
Enforce the build to pull-in meson from stretch-backports, i.e. a meson version that is newer than 0.40.0.
Reasoning: if you want to build your package against debhelper (>= 11~) from stretch-backports it will use the --wrap-mode option when invoking meson. However, this option only got added in meson 0.40.0. So you need to make sure, the meson version from stretch-backports gets pulled in, too, for your build. The build will fail when using the meson version that we find in Debian stretch.