Make generate-groups.sh and generate-knative.sh executable conditiona…

…lly (#338)

The codegen-library.sh script might be executed within a container that
doesn't run as root in which case changing permissions is not allowed
and the whole scripts fails.
This change gives opportunity to set the permissions in advance (e.g.
during docker build) and then run this script successfully.

codegen-library.sh

@@ -31,5 +31,5 @@ export GOBIN=${GOPATH}/bin # Set GOBIN explicitly as deepcopy-gen is installed b
 export CODEGEN_PKG=${CODEGEN_PKG:-$(cd ${REPO_ROOT_DIR}; ls -d -1 ./vendor/k8s.io/code-generator 2>/dev/null || echo ../code-generator)}
 export KNATIVE_CODEGEN_PKG=${KNATIVE_CODEGEN_PKG:-$(cd ${REPO_ROOT_DIR}; ls -d -1 ./vendor/knative.dev/pkg 2>/dev/null || echo "${REPO_ROOT_DIR}")}
 
-chmod +x ${CODEGEN_PKG}/generate-groups.sh
-chmod +x ${KNATIVE_CODEGEN_PKG}/hack/generate-knative.sh
+[ -x ${CODEGEN_PKG}/generate-groups.sh ] || chmod +x ${CODEGEN_PKG}/generate-groups.sh
+[ -x ${KNATIVE_CODEGEN_PKG}/hack/generate-knative.sh ] || chmod +x ${KNATIVE_CODEGEN_PKG}/hack/generate-knative.sh