cgo file and .c .h with different directory may cause go build failed

[lcmmhcc]

according to https://github.com/golang/go/blob/master/src/cmd/cgo/doc.go#L109

including the cgo file and use go mod vendor is an easy way to reproduce it.

issues https://github.com/golang/go/issues/26366

[tarakby]

The cgo files in the go build are actually only https://github.com/supranational/blst/blob/master/bindings/go/cgo_assembly.S and https://github.com/supranational/blst/blob/master/bindings/go/cgo_server.c. All the source directory code is "copied" thanks to the include directive.