env/corellium: mention cgo and clangwrapper must be used
env/corellium: mention cgo and clangwrapper must be used

Change-Id: Id40da315377b4f201ed9b9ac256e965e3bfa913d
Reviewed-on: https://go-review.googlesource.com/c/build/+/367114
Reviewed-by: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>
Reviewed-by: Cherry Mui <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>

golang/build,golang/build,golang/build,golang/build