Enable kokoro (presubmit) testing for the Go unified builder
Enable kokoro (presubmit) testing for the Go unified builder

PiperOrigin-RevId: 442920242
Change-Id: I971f2262002a4413136c0add2f24de2ec012f7c8

GoogleCloudPlatform/buildpacks,GoogleCloudPlatform/buildpacks,GoogleCloudPlatform/buildpacks,GoogleCloudPlatform/buildpacks