Configure the static plugin header, reduce rebuilds

Every time CMake is invoked it will write out the file with static
plugins, configuring the file seen by the build system will reduce
unnecessary rebuilds by preserving the timestamp unless something
actually changes.

Change-Id: I026cc74867ba00baa9d0490fd7489240446cdaf4
Merge topic 'static-plugins-rebuilds' into master

2632ec86 Configure the static plugin header, reduce rebuilds