Separated out from bug 1486038 comment 1. aarch64-windows builds satisfy both `CONFIG["OS_TARGET"] == "WINNT"` and `CONFIG["CPU_ARCH"] == "aarch64"` in moz.build, so we get both the fixed- and floating-point versions of noise suppression, which cause all sorts of build collisions. https://searchfox.org/mozilla-central/rev/3c85ea2f8700ab17e38b82d77cd44644b4dae703/media/webrtc/trunk/webrtc/modules/audio_processing/audio_processing_c_gn/moz.build#158,168 This line suggests that the fixed-point code is the one we'd prefer: https://searchfox.org/mozilla-central/rev/3c85ea2f8700ab17e38b82d77cd44644b4dae703/media/webrtc/trunk/webrtc/build/webrtc.gni#97 I'm not quite sure how the moz.build logic maps back to gn.

Re-building the moz.build files after getting aarch64 gn outputs ought to fix all of these issues in one go.