Add GOBIN to PATH in Makefile

[alexshtin]

What changed?
GOBIN variable value is added to PATH env variable.

Why?
Some users don't have default go bin directory in PATH variable. This leads to failure in proto compiler and other go tools. With this fix binaries will always be accessible. Fix is based on the doc:

The install directory is controlled by the GOPATH and GOBIN environment variables. If GOBIN is set, binaries are installed to that directory. If GOPATH is set, binaries are installed to the bin subdirectory of the first directory in the GOPATH list. Otherwise, binaries are installed to the bin subdirectory of the default GOPATH ($HOME/go or %USERPROFILE%\go).

How did you test it?
Run it locally.

Potential risks
No risks.