I installed Gnome Builder from Discover. I am not sure if this is the latest version or not, but the version is 3.30.1. I clicked new project and chose C# GTK application. Without changing anything, I pressed the build button, and build failed.
The message was,
Already on 'master'
The Meson build system
Version: 0.46.0 Source dir: /run/build/gtk-sharp3
Build dir: /run/build/gtk-sharp3/_flatpak_build
Build type: native build
meson_options.txt:2:0: ERROR: Unknown type feature.
A full log can be found at /run/build/gtk-sharp3/_flatpak_build/meson-logs/meson-log.txt Error: module gtk-sharp3: Child process exited with code 1
I had searched Google, and it seemed to be that the message was because Meson's version was below 47. But the problem is, I am not sure where this "0.46.0" is coming from. I have examined all files in the project, and none of the files had that version string. I installed Meson manually, and its version was 0.48.1. Still, I got the same message. I uninstalled Meson, and still I got the same message.
It seems almost as if Gnome Builder ignores system-wide settings, and has its own copy of Meson 0.46.0 somewhere. How to change it?
Builder is probably building your application against a particular Flatpak runtime, which includes a particular version of Meson independent from what's installed in your host system. In the Build Settings panel you can select a different runtime or build against the host system.