Trim down Emscripten SDK asset size

These cuts reduce the number of files by 2/3 and the size by 1/3

There's not too much more that could be trimmed - now the size
is dominated by the specially compiled LLVM/Clang binaries

Bug: skia:7186
Change-Id: Ie88fb6f2277eafbefac0f676daaca809dcb53f62
Reviewed-on: https://skia-review.googlesource.com/107061
Reviewed-by: Ben Wagner <benjaminwagner@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
3 files changed