Add wasm32-experimental-emscripten to wasm builder

This modifies the builder to download and use the LLVM tools from the
last known good build on the WebAssembly buildbot waterfall, since these
tools are built with the WebAssembly LLVM backend enabled.

Author: tlively

src/ci/docker/disabled/wasm32/Dockerfile

@@ -11,7 +11,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
   cmake \
   sudo \
   gdb \
-  xz-utils
+  xz-utils \
+  jq \
+  bzip2
 
 # dumb-init
 COPY scripts/dumb-init.sh /scripts/
@@ -22,6 +24,10 @@ COPY scripts/emscripten.sh /scripts/
 RUN bash /scripts/emscripten.sh
 COPY disabled/wasm32/node.sh /usr/local/bin/node
 
+# cache
+COPY scripts/sccache.sh /scripts/
+RUN sh /scripts/sccache.sh
+
 # env
 ENV PATH=$PATH:/emsdk-portable
 ENV PATH=$PATH:/emsdk-portable/clang/e1.37.13_64bit/
@@ -32,13 +38,9 @@ ENV EM_CONFIG=/emsdk-portable/.emscripten
 
 ENV TARGETS=wasm32-unknown-emscripten,wasm32-experimental-emscripten
 
-ENV RUST_CONFIGURE_ARGS --target=$TARGETS --experimental-targets=WebAssembly
+ENV RUST_CONFIGURE_ARGS --target=$TARGETS
 
 ENV SCRIPT python2.7 ../x.py test --target $TARGETS
 
-# cache
-COPY scripts/sccache.sh /scripts/
-RUN sh /scripts/sccache.sh
-
 # init
 ENTRYPOINT ["/usr/bin/dumb-init", "--"]

src/ci/docker/scripts/emscripten.sh

@@ -27,30 +27,38 @@ exit 1
   set -x
 }
 
+# Download emsdk
 cd /
 curl -L https://s3.amazonaws.com/mozilla-games/emscripten/releases/emsdk-portable.tar.gz | \
     tar -xz
 
+# Download last known good emscripten from WebAssembly waterfall
+BUILD=$(curl -L https://storage.googleapis.com/wasm-llvm/builds/linux/lkgr.json | \
+    jq '.build | tonumber')
+curl -L https://storage.googleapis.com/wasm-llvm/builds/linux/$BUILD/wasm-binaries.tbz2 | \
+    hide_output tar xvkj
+
+# node 8 is required to run wasm
+cd /
+curl -L https://nodejs.org/dist/v8.0.0/node-v8.0.0-linux-x64.tar.xz | \
+    tar -xJ
+
 cd /emsdk-portable
 ./emsdk update
 hide_output ./emsdk install sdk-1.37.13-64bit
 ./emsdk activate sdk-1.37.13-64bit
 
+# Make emscripten use wasm-ready node and LLVM tools
+echo "NODE_JS='/node-v8.0.0-linux-x64/bin/node'" >> /root/.emscripten
+echo "LLVM_ROOT='/wasm-install/bin'" >> /root/.emscripten
+
+# Make emsdk usable by any user
+cp /root/.emscripten /emsdk-portable
+chmod a+rxw -R /emsdk-portable
+
 # Compile and cache libc
 source ./emsdk_env.sh
 echo "main(){}" > a.c
 HOME=/emsdk-portable/ emcc a.c
 HOME=/emsdk-portable/ emcc -s WASM=1 a.c
 rm -f a.*
-
-# Make emscripten use Rust's LLVM
-echo "LLVM_ROOT='/checkout/obj/build/x86_64-unknown-linux-gnu/llvm/bin'" >> /root/.emscripten
-
-# Make emsdk usable by any user
-cp /root/.emscripten /emsdk-portable
-chmod a+rxw -R /emsdk-portable
-
-# node 8 is required to run wasm
-cd /
-curl -L https://nodejs.org/dist/v8.0.0/node-v8.0.0-linux-x64.tar.xz | \
-    tar -xJ