Add support for GOBIN to generate-groups.sh.

This still honors `$GOPATH` if it is set, but no longer requires it to be set, and also honors `$GOBIN` if it is set.

Fixes https://github.com/kubernetes/code-generator/issues/87

Author: porridge

staging/src/k8s.io/code-generator/generate-groups.sh

@@ -52,6 +52,8 @@ shift 4
   cd "$(dirname "${0}")"
   go install ./cmd/{defaulter-gen,client-gen,lister-gen,informer-gen,deepcopy-gen}
 )
+# We expect the above commands to get installed here:
+gobin="$(go env GOBIN)" 
 
 function codegen::join() { local IFS="$1"; shift; echo "$*"; }
 
@@ -68,22 +70,22 @@ done
 
 if [ "${GENS}" = "all" ] || grep -qw "deepcopy" <<<"${GENS}"; then
   echo "Generating deepcopy funcs"
-  "${GOPATH}/bin/deepcopy-gen" --input-dirs "$(codegen::join , "${FQ_APIS[@]}")" -O zz_generated.deepcopy --bounding-dirs "${APIS_PKG}" "$@"
+  "${gobin}/deepcopy-gen" --input-dirs "$(codegen::join , "${FQ_APIS[@]}")" -O zz_generated.deepcopy --bounding-dirs "${APIS_PKG}" "$@"
 fi
 
 if [ "${GENS}" = "all" ] || grep -qw "client" <<<"${GENS}"; then
   echo "Generating clientset for ${GROUPS_WITH_VERSIONS} at ${OUTPUT_PKG}/${CLIENTSET_PKG_NAME:-clientset}"
-  "${GOPATH}/bin/client-gen" --clientset-name "${CLIENTSET_NAME_VERSIONED:-versioned}" --input-base "" --input "$(codegen::join , "${FQ_APIS[@]}")" --output-package "${OUTPUT_PKG}/${CLIENTSET_PKG_NAME:-clientset}" "$@"
+  "${gobin}/client-gen" --clientset-name "${CLIENTSET_NAME_VERSIONED:-versioned}" --input-base "" --input "$(codegen::join , "${FQ_APIS[@]}")" --output-package "${OUTPUT_PKG}/${CLIENTSET_PKG_NAME:-clientset}" "$@"
 fi
 
 if [ "${GENS}" = "all" ] || grep -qw "lister" <<<"${GENS}"; then
   echo "Generating listers for ${GROUPS_WITH_VERSIONS} at ${OUTPUT_PKG}/listers"
-  "${GOPATH}/bin/lister-gen" --input-dirs "$(codegen::join , "${FQ_APIS[@]}")" --output-package "${OUTPUT_PKG}/listers" "$@"
+  "${gobin}/lister-gen" --input-dirs "$(codegen::join , "${FQ_APIS[@]}")" --output-package "${OUTPUT_PKG}/listers" "$@"
 fi
 
 if [ "${GENS}" = "all" ] || grep -qw "informer" <<<"${GENS}"; then
   echo "Generating informers for ${GROUPS_WITH_VERSIONS} at ${OUTPUT_PKG}/informers"
-  "${GOPATH}/bin/informer-gen" \
+  "${gobin}/informer-gen" \
            --input-dirs "$(codegen::join , "${FQ_APIS[@]}")" \
            --versioned-clientset-package "${OUTPUT_PKG}/${CLIENTSET_PKG_NAME:-clientset}/${CLIENTSET_NAME_VERSIONED:-versioned}" \
            --listers-package "${OUTPUT_PKG}/listers" \