[Buildroot] [PATCH v3] Post-image addition, and customize removal

[Thomas Petazzoni]

Hello,

Here is the third version of the post-image addition and customize
removal patch set.

Compared to version 2:

 * Slightly adjust the post-image config option prompt to use "Custom
   scripts" instead of "Custom script"

 * Add Acked-by from Samuel Martin

 * Slightly improve the documentation as per the suggestion of Samuel.

 * Add one patch to change "Custom script" to "Custom scripts" for the
   post-build scripts config option.

Best regards,

Thomas