installs gcc and g++, because "it is not uncommon for a go build to depend on gcc and g++"
We had the same problem for the new Java stack: mvn is not installed in the JDT LS sidecar. The decision in that case has been to use a dedicated runtime container (based on the official maven image, gradle image etc...). The user is not supposed to open a terminal in the JDT LS sidecar but to open it in runtime container. The workspaces commands will be run against the runtime container as well.
The Java stack solution is not ideal because: 1) the jdk versions of the runtime and the sidecar may not match leading to some inconsistencies 2) we need to start 2 containers and that means more resources + longer startup time.
But Eugene PR's solution is not ideal neither because 1) as Thomas said users will need to build and distribute their own sidecars 2) the main ws.next promise was to let user reuse their runtimes and we are not respecting it
So even if the Java stack solution is not perfect it's currently the best trade-off we can propose.
