Subdir option seems to be ineffective

[erin-desu]

I have a project and its meson.build is an a subdirectory. The subdirectory can be set by subdir option in module's definition. flatpak-builder respects this option normally, but this extensions seems to completely ignore.

>>> flatpak build --share=network --filesystem=/var/home/erin/Projekty/deploynt --filesystem=/var/home/erin/Projekty/deploynt/.flatpak/repo --env=PATH=/usr/lib/sdk/rust-stable/bin:/usr/lib/sdk/llvm18/bin:/var/home/erin/.local/bin:/var/home/erin/.local/share/cargo/bin:/var/lib/flatpak/exports/bin/:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/sbin:/bin:/app/bin:/usr/bin --env=LD_LIBRARY_PATH=/app/lib --env=PKG_CONFIG_PATH=/app/lib/pkgconfig:/app/share/pkgconfig:/usr/lib/pkgconfig:/usr/share/pkgconfig --filesystem=/var/home/erin/Projekty/deploynt/_build /var/home/erin/Projekty/deploynt/.flatpak/repo meson --prefix /app _build

ERROR: Neither source directory '_build' nor build directory None contain a build file meson.build.
WARNING: Running the setup command as `meson [options]` instead of `meson setup [options]` is ambiguous and deprecated.
>>> Error: Child process exited with code 1

[SeaDve]

This seems duplicate/related to #129