Upgrade to Emscripten 3.1.27

This is the first release that's based on Ubuntu 22.04 LTS (jammy) that upgrades CMake from 3.16.3 to 3.22.1.

This is newer than emscripten 3.1.14 which is the version listed on https://doc.qt.io/qt-6/wasm.html

This also gives a new Emscripten toolchain location. Also, backports are no longer needed after the Ubuntu upgrade.

image/Dockerfile

@@ -1,5 +1,5 @@
 # Based on https://github.com/emscripten-core/emsdk/tree/master/docker
-FROM emscripten/emsdk:1.39.10 AS qtbuilder
+FROM emscripten/emsdk:3.1.27 AS qtbuilder
 
 RUN mkdir -p /development
 WORKDIR /development
@@ -24,7 +24,7 @@ RUN make -j `nproc`
 RUN make install
 
 
-FROM emscripten/emsdk:1.39.10
+FROM emscripten/emsdk:3.1.27
 
 # install GE root certificate
 # must be downloaded from https://static.gecirtnotification.com/browser_remediation/sop_server_v1.html and copied into container first
@@ -44,10 +44,6 @@ RUN apt-get update && apt-get -y install \
     libeigen3-dev    \
     libboost-dev
 
-# Activate backports for more recent version of CMake
-RUN echo "deb http://deb.debian.org/debian buster-backports main" > /etc/apt/sources.list.d/backports.list && apt-get update
-RUN apt-get -t buster-backports -y install cmake                   # from https://packages.debian.org/buster-backports/cmake
-
 # Make symlinks to avoid adding /usr/include to include dirs.
 RUN mkdir -p /project/dependencies/include && mkdir -p /project/dependencies/lib && \
     ln -s /usr/include/boost   /project/dependencies/include/boost  && \
@@ -62,4 +58,4 @@ RUN mkdir -p /project/dependencies/include && mkdir -p /project/dependencies/lib
 WORKDIR /project/build
 
 # Default build command
-CMD cmake -DCMAKE_TOOLCHAIN_FILE=/emsdk/emscripten/sdk/cmake/Modules/Platform/Emscripten.cmake -DCMAKE_BUILD_TYPE=Release -G "Unix Makefiles" -DCMAKE_PREFIX_PATH=/project/Qt /project/source && make
+CMD cmake -DCMAKE_TOOLCHAIN_FILE=/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -DCMAKE_BUILD_TYPE=Release -G "Unix Makefiles" -DCMAKE_PREFIX_PATH=/project/Qt /project/source && make