WIP: Fix build

Dockerfile

@@ -1,4 +1,4 @@
-FROM emscripten/emsdk:5.0.1 as build
+FROM emscripten/emsdk:5.0.1 AS build
 
 ARG FFMPEG_VERSION=8.0.1
 ARG X264_COMMIT=b35605a
@@ -7,7 +7,12 @@ ARG LAME_VERSION=3.100
 ARG PREFIX=/opt/ffmpeg
 ARG MAKEFLAGS="-j4"
 
-RUN apt-get update && apt-get install -y autoconf libtool build-essential
+RUN wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | sudo tee /etc/apt/trusted.gpg.d/apt.llvm.org.asc
+RUN echo "deb https://apt.llvm.org/jammy/ llvm-toolchain-jammy-20 main\ndeb-src https://apt.llvm.org/jammy/ llvm-toolchain-jammy-20 main" > /etc/apt/sources.list.d/llvm.list
+RUN apt-get update
+RUN apt-get install -y libllvm-20-ocaml-dev libllvm20 llvm-20 llvm-20-dev llvm-20-runtime
+RUN apt-get install -y libclang-rt-20-dev-wasm32 libclang-rt-20-dev-wasm64 libc++-20-dev-wasm32 libc++abi-20-dev-wasm32 libclang-rt-20-dev-wasm32 libclang-rt-20-dev-wasm64
+RUN apt-get update && apt-get install -y autoconf libtool build-essential pkgconf
 
 # libx264
 WORKDIR /tmp/
@@ -49,6 +54,7 @@ RUN wget -O ffmpeg-${FFMPEG_VERSION}.tar.gz http://ffmpeg.org/releases/ffmpeg-${
 
 ARG CFLAGS="-s USE_PTHREADS=1 -O3 -I${PREFIX}/include"
 ARG LDFLAGS="$CFLAGS -L${PREFIX}/lib -s INITIAL_MEMORY=33554432"
+ENV EM_PKG_CONFIG_PATH="${PREFIX}/lib/pkgconfig"
 
 # Compile ffmpeg.
 WORKDIR /tmp/ffmpeg-${FFMPEG_VERSION}
@@ -70,7 +76,6 @@ RUN emconfigure ./configure \
   --enable-avdevice \
   --enable-avutil \
   --enable-swresample \
-  --enable-postproc \
   --enable-swscale \
   --enable-protocol=file \
   --enable-decoder=h264,aac,pcm_s16le,mp3 \