This commit updates the "browser-asmjs" images to avoid systematic
rebuild of emscripten sdk. Instead, it introduces dependency on the
image maintained by @trzeci
Note also:
* emscripten sdk updated from 1.36.7 to 1.36.14
* symlinking of "/bin/bash" as "/bin/sh" is reverted. This ensures other
images including file like "common.debian" and relying on standard "sh"
behavior will work as expected.
* workaround associated with CMakeForceCompiler has been removed from
Dockerfile. Emscripten as been fixed.
See https://github.com/kripken/emscripten/pull/4477
* we will revisit once official images are available.
See https://github.com/kripken/emscripten/issues/4682
