plugin-compiler: use a dynamic package path (#3196)
plugin-compiler: use a dynamic package path (#3196)

Workaround for #3195.

To test this without having to rebuild the `tyk-plugin-compiler` image, the `build.sh` can be replaced on runtime using the volume flag:
```
$ docker run --rm -v `pwd`/build.sh:/build.sh -v `pwd`:/plugin-source tykio/tyk-plugin-compiler:v2.9.4.2 plugin1.so
``` 
With this fix, the scenario described in the original ticket will perform as expected, allowing the usage of multiple Docker-built Go plugins.
lonelycode/tyk,lonelycode/tyk,lonelycode/tyk