Allow the buildpack to skip

[dmikusa]

Describe the Enhancement

In some cases, you may have an off-the-shelf WAR file that you are trying to deploy. It may contain a Main-Class entry for "reasons" and because it's off-the-shelf you cannot change that easily. In this scenario, the executable-jar buildpack will run first and see the Main-Class and incorrectly try to run it.

We should have a way to override the default behavior to tell executable-jar to skip.

Possible Solution

Add an env variable that disables the executable-jar buildpack, like BP_EXECUTABLE_JAR_DISABLED. It would default to false. When true, it would just cause the buildpack to fail detection, which in turn would make it skip.

Motivation

See Above.