User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0

Steps to reproduce:

I wanted to compile firefox-76.0_beta2 for amd64 on linux/gnu (gentoo)

Actual results:

the build failed with this error:

6:47.95 In file included from Unified_cpp_webrtc_vp9_gn0.cpp:20:
6:47.95 /var/tmp/portage/www-client/firefox-76.0_beta2/work/firefox-76.0/media/webrtc/trunk/webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc: In member function 'int webrtc::VP9EncoderImpl::InitAndSetControlSettings(const webrtc::VideoCodec*)':
6:47.98 /var/tmp/portage/www-client/firefox-76.0_beta2/work/firefox-76.0/media/webrtc/trunk/webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc:447:7: error: 'vpx_svc_frame_drop_t' was not declared in this scope; did you mean 'vpx_enc_frame_flags_t'?
6:47.99 447 | vpx_svc_frame_drop_t svc_drop_frame;
6:47.99 | ^~~~~~~~~~~~~~~~~~~~
6:47.99 | vpx_enc_frame_flags_t
6:47.99 /var/tmp/portage/www-client/firefox-76.0_beta2/work/firefox-76.0/media/webrtc/trunk/webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc:448:7: error: 'svc_drop_frame' was not declared in this scope
6:48.00 448 | svc_drop_frame.framedrop_mode = CONSTRAINED_LAYER_DROP;
6:48.00 | ^~~~~~~~~~~~~~
6:48.00 /var/tmp/portage/www-client/firefox-76.0_beta2/work/firefox-76.0/media/webrtc/trunk/webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc:448:39: error: 'CONSTRAINED_LAYER_DROP' was not declared in this scope
6:48.00 448 | svc_drop_frame.framedrop_mode = CONSTRAINED_LAYER_DROP;
6:48.00 | ^~~~~~~~~~~~~~~~~~~~~~
6:48.00 In file included from /usr/include/vpx/vp8.h:33,
6:48.00 from /usr/include/vpx/vp8cx.h:18,
6:48.00 from /var/tmp/portage/www-client/firefox-76.0_beta2/work/firefox-76.0/ff/dist/system_wrappers/vpx/vp8cx.h:3,
6:48.00 from /var/tmp/portage/www-client/firefox-76.0_beta2/work/firefox-76.0/media/webrtc/trunk/webrtc/modules/video_coding/codecs/vp9/vp9_impl.h:21,
6:48.00 from /var/tmp/portage/www-client/firefox-76.0_beta2/work/firefox-76.0/media/webrtc/trunk/webrtc/modules/video_coding/codecs/vp9/screenshare_layers.h:13,
6:48.00 from /var/tmp/portage/www-client/firefox-76.0_beta2/work/firefox-76.0/media/webrtc/trunk/webrtc/modules/video_coding/codecs/vp9/screenshare_layers.cc:10,
6:48.00 from Unified_cpp_webrtc_vp9_gn0.cpp:2:
6:48.01 /var/tmp/portage/www-client/firefox-76.0_beta2/work/firefox-76.0/media/webrtc/trunk/webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc:453:35: error: 'VP9E_SET_SVC_FRAME_DROP_LAYER' was not declared in this scope
6:48.01 453 | vpx_codec_control(encoder_, VP9E_SET_SVC_FRAME_DROP_LAYER,
6:48.01 | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
6:48.01 /var/tmp/portage/www-client/firefox-76.0_beta2/work/firefox-76.0/media/webrtc/trunk/webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc:453:7: error: 'vpx_codec_control_VP9E_SET_SVC_FRAME_DROP_LAYER' was not declared in this scope; did you mean 'vpx_codec_control_VP9E_SET_SVC_LAYER_ID'?
6:48.01 453 | vpx_codec_control(encoder_, VP9E_SET_SVC_FRAME_DROP_LAYER,
6:48.01 | ^~~~~~~~~~~~~~~~~
6:48.01 gmake[4]: *** [/var/tmp/portage/www-client/firefox-76.0_beta2/work/firefox-76.0/config/rules.mk:752: Unified_cpp_webrtc_vp9_gn0.o] Error 1
6:48.01 gmake[4]: Leaving directory '/var/tmp/portage/www-client/firefox-76.0_beta2/work/firefox-76.0/ff/media/webrtc/trunk/webrtc/modules/video_coding/webrtc_vp9_gn'
6:48.01 gmake[3]: *** [/var/tmp/portage/www-client/firefox-76.0_beta2/work/firefox-76.0/config/recurse.mk:74: media/webrtc/trunk/webrtc/modules/video_coding/webrtc_vp9_gn/target-objects] Error 2
6:48.01 gmake[3]: *** Waiting for unfinished jobs....

the full build.log is attached

Expected results:

the build should have succeeded.

on closer inspection, this happens since the config scripts don't error out when there's still libvpx-1.7 to be build against