====== Named configurations ======

Named configurations can be specified via the ''CONFIG=...'' build
parameter.

For headers in ''config/*.h'' which support named configurations, the following files are included when building with ''CONFIG=**<name>**'':

  * ''config/defaults/<platform>.h'' (e.g. ''config/defaults/pcbios.h'')
  * ''config/<header>.h''
  * ''config/**<name>**/<header>.h'' (only if the directory ''config/**<name>**'' exists)
  * ''config/local/<header>.h'' (autocreated if necessary)
  * ''config/local/**<name>**/<header>.h'' (autocreated if necessary)

This mechanism allows for predefined named configurations to be checked in to the source tree, as a directory ''config/**<name>**'' containing all of the required header files.

The mechanism also allows for users to define multiple local configurations, by creating header files in the directory ''config/local/**<name>**''.

Note that the ''config/*.h'' files which are used only to configure internal iPXE APIs (e.g. ''config/umalloc.h'') cannot be modified via a named configuration.  This avoids rebuilding the entire iPXE codebase whenever switching to a different named configuration.