Dockerfile definition and helper scripts related to preparing a toolchain image able to produce WASM binaries

Includes emscripten toolchain like also precompiled libraries:

• boost
• openssl
• sec256k1-zkp

scripts/bash/emscripten/prepare_boost.sh

 #! /bin/bash
 
+echo "Building Boost..."
+
 set -xeuo pipefail
 
 TMP_SRC=${1:?"Missing arg #1 to specify source temp directory"}
@@ -44,3 +46,5 @@ printf "using clang : emscripten : emcc -s USE_ZLIB=1 -s USE_ICU=0 : <archiver>e
   --with-regex \
   --with-system \
   install
+
+echo "Boost build finished"
\ No newline at end of file