facedetect not build from source

[Marc]

I have gstreamer 1.18.5 build from git generating this error

0:00:00.030326651  9847      0x12c6040 ERROR            faceoverlay gstfaceoverlay.c:147:gst_face_overlay_create_children:<GstFaceOverlay at 0x136a040> facedetect element not found (opencv plugin)

The faceoverlay is being build, it looks like the opencv is correctly detected[1]. So it I am probably missing some other library. How can I see what library I am missing for building the facedect? I am not really familiar with the meson build / ninja -C build options and discovering dependencies.

[1]
Run-time dependency opencv found: YES 3.4.6
Dependency opencv found: YES 3.4.6 (cached)
Has header "opencv2/bgsegm.hpp" : YES
Has header "opencv2/calib3d.hpp" : YES
Has header "opencv2/core.hpp" : YES
Has header "opencv2/imgproc.hpp" : YES
Has header "opencv2/objdetect.hpp" : YES
Has header "opencv2/opencv.hpp" : YES
Has header "opencv2/video.hpp" : YES