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=${1:?"Missing arg #1 to specify source temp directory"}
+INSTALL_PREFIX=${2:?"Missing arg #2 to specify prebuilt libraries install prefix"}
+
+echo "Entering directory: ${TMP_SRC}/boost/tools/build"
+
+cd "${TMP_SRC}/boost/tools/build"
+
+# Clean local mods if any
+git checkout .
+# to fix ambigous generators specific to SEARCH_LIB
+git apply /home/emscripten/scripts/emscripten_toolset.patch
+
+rm -vrf "${TMP_SRC}/boost_build/"
+
+mkdir -vp "${TMP_SRC}/boost_build/"
+
+echo "Entering directory: ${TMP_SRC}/boost"
+
+cd "${TMP_SRC}/boost"
+
+./bootstrap.sh --without-icu --prefix="${INSTALL_PREFIX}"
+
+printf "using clang : emscripten : emcc -s USE_ZLIB=1 -s USE_ICU=0 : <archiver>emar <ranlib>emranlib <linker>emlink <cxxflags>\"-std=c++11 -s USE_ICU=0\" ;" | tee -a ./project-config.jam >/dev/null
+
+./b2 \
+  --build-dir="${TMP_SRC}/boost_build/" \
+  --prefix="${INSTALL_PREFIX}" \
+  -j "$(nproc)" \
+  -q \
+  runtime-link=static \
+  link=static \
+  toolset=clang-emscripten \
+  variant=release \
+  threading=single \
+  --with-atomic \
+  --with-chrono \
+  --with-date_time \
+  --with-filesystem \
+  --with-program_options \
+  --with-regex \
+  --with-system \
+  install
+
+echo "Boost build finished."
\ No newline at end of file