Fixes for 0.15 (#1449)

* Wasmtime 0.15.0 and Cranelift 0.62.0. (#1398)

* Bump more ad-hoc versions.

* Add build.rs to wasi-common's Cargo.toml.

* Update the env var name in more places.

* Remove a redundant echo.

scripts/publish-wasmtime.sh

@@ -53,4 +53,4 @@ for cargo_toml in \
     echo sleep 20
 done
 
-echo echo git tag v$(grep "version =" Cargo.toml | head -n 1 | cut -d '"' -f 2)
+echo git tag v$(grep "version =" Cargo.toml | head -n 1 | cut -d '"' -f 2)