Dependencies must be external dependencies (meson warning)

I tried to build GStreamer from source. I git cloned the project and switched to branch 1.16. Ran mkdir build, cd build, meson … and I ended up with the following warning :

…/subprojects/gst-plugins-base/ext/gl/meson.build:117:26: ERROR: Dependencies must be external dependencies

Any idea how can I fix this ?

total noob so i can’t be of much help beyond this, but i hit the same wall. install libdrm-dev (sudo apt install libdrm-dev) then run the build command again.