fteqw-docker: Add emscripten SDK setup

fteqw-docker/Dockerfile

@@ -1,11 +1,19 @@
+# Source Ubuntu for better package sourcing
 FROM ubuntu:18.04
 
+# Currently broken macOS SDK
 COPY MacOSX10.14.sdk.tar.xz /
 
-WORKDIR /fteqw
+# Set up some EMSDK variables
+ARG EMSCRIPTEN_VERSION=tot
+ENV EMSDK /emsdk
 
+WORKDIR /
+
+# For building 32 bit binaries
 RUN dpkg --add-architecture i386
 
+# First round of apt spam
 RUN apt-get update \
  && apt-get install -y \
     build-essential \
@@ -41,12 +49,28 @@ RUN apt-get update \
     mingw-w64-tools \
     linux-libc-dev:i386
 
+# EMSDK apt spam (2nd round)
+RUN apt-get install -y \
+    binutils \
+    ca-certificates \
+    file \
+    python3 \
+    python3-pip
+
+# Third wave + delete apt list to save space
 RUN apt-get install -y \
     gcc-arm-linux-gnueabihf \
     gcc-aarch64-linux-gnu \
     binutils-aarch64-linux-gnu \
  && rm -rf /var/lib/apt/lists/*
 
+# Proceed with EMSDK install
+RUN cd / && \
+    git clone https://github.com/emscripten-core/emsdk && \
+    cd ${EMSDK} && \
+    ./emsdk install ${EMSCRIPTEN_VERSION}
+
+# Set up OSXCross with the macOS SDK
 RUN cd /opt \
  && git clone https://github.com/tpoechtrager/osxcross.git \
  && cd osxcross \
@@ -54,4 +78,14 @@ RUN cd /opt \
  && mv /MacOSX10.14.sdk.tar.xz tarballs \
  && PORTABLE=1 UNATTENDED=1 ./build.sh
 
-ENV PATH $PATH:/opt/osxcross/target/bin
+# OSXCross path
+ENV PATH $PATH:/opt/osxcross/target/bin
+
+# Edit path again, but for EMSDK
+ENV EMSDK=/emsdk \
+    EM_CONFIG=/emsdk/.emscripten \
+    EMSDK_NODE=/emsdk/node/14.18.2_64bit/bin/node \
+    PATH="/emsdk:/emsdk/upstream/emscripten:/emsdk/upstream/bin:/emsdk/node/14.18.2_64bit/bin:${PATH}"
+
+# (Finally) create a config for emcc
+RUN emcc --generate-config