Update to current webrtc library

This is from the upstream library commit id
3326535126e435f1ba647885ce43a8f0f3d317eb, corresponding to Chromium
88.0.4290.1.

webrtc/modules/third_party/fft/meson.build

@@ -0,0 +1,13 @@
+fft_sources = ['fft.c']
+
+libfft = static_library('libfft',
+    fft_sources,
+    dependencies: common_deps,
+    include_directories: webrtc_inc,
+    cpp_args : common_cxxflags
+)
+
+fft_dep = declare_dependency(
+    link_with: libfft
+)
+