tonic_build unusable without rustfmt

[TheBlueMatt]

When trying to compile a project that uses tonic_build to compile protobufs ([1]) on a machine without rustup (i.e. rustfmt is not available) I initially get the "error running rustfmt" error in the build script. I tried disabling default-features and re-enabling the "transport" and "prost" features and building that way, but it doesn't seem to actually compile things when doing that.

It depends on tonic-build version 0.6 for the build-script. The error is platform-independent (at least on Linux).

[1] https://github.com/L2-Technology/sensei/

[TheBlueMatt]

Looks like this will be resolved once #904 ships.

[davidpdrsn]

That shipped in tonic-build 0.7