1. A method comprising: obtaining, at a computing device, a package of information defining an extension to an application program interface (API) of a runtime, the package of information including native program code configured to expose services of different hardware platforms that are not exposed by the API and descriptors that identify the different hardware platforms supported by the extension; obtaining, at the computing device, a declaration of a target hardware platform for an application program that employs the extension; comparing, at the computing device, the declaration of the target hardware platform for the application program with the descriptors that identify the different hardware platforms supported by the extension; and generating, at the computing device, an installable package for the application program if the target hardware platform is supported by the extension, the installable package configured to enable the application program to access services of the target hardware platform; or providing a notification if the target hardware platform is not supported by the extension.