Export all files as @emscripten_bin_{platform}//:all

[attilaolah]

The BUILD_FILE_CONTENT_TEMPLATE in bazel/emscripten_deps.bzl currently currently exports a selection of files used by the CC toolchain that is configured here.

I'm facing a problem while creating Configure, Make & CMake toolchains using Emscripten via rules_foreign_cc, where I need access to other files from the @emscripten_bin_linux repository, namely emconfigure[.py], emmake[.py] and emcmake[.py]. My current approach is to patch this repo (@emsdk) to modify the BUILD_FILE_CONTENT_TEMPLATE to export these files too.

Would you be accepting a pull request that simply adds an :all target to @emscripten_bin_linux and friends, which could then be used by toolchain developers to access other files from the binary repo? That would make my life easier.