Disabling all warnings during a Headless PDE build

Question

How do you disable all compiler warnings from headless PDE builds of Eclipse plugins?

I know I can do something like this in the build.properties:

javacWarnings..=-deadCode

To disable specific warnings by ID, but the documentation is not very explicit.

I have 2 questions:

1. How do I disable all warnings not just specific ones?
2. Can this be placed in the build.properties for the entire build, or must this be placed in the build.properties for each plugin?