Rollup merge of #40821 - arielb1:fix-emscripten, r=TimNN
Rollup merge of #40821 - arielb1:fix-emscripten, r=TimNN

try to fix the build on emscripten

The "upstream" emscripten tar.gz now extracts to `emsdk-portable` instead of `emsdk_portable`, breaking our CI. It might be better to vendor a specific version of emscripten instead of using the latest, but I could not find a good way of doing that.

r? @alexcrichton

aidancully/rust,graydon/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,GBGamer/rust,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust