Remove Trebuchet overlay

This reverts commit 83582bd497892fe12b1f1d07d0950d751350cd9d.

Change-Id: I73f61dbdec039cf20f8da9cddb73f406b78c18d4
Use "include" instead of "-include" wherever appropriate

* When using "-include", make ignores a makefile which does not
  exist, with no error message.
* Use "include" for all makefiles which are essential for a
  working build.

Change-Id: Ic00ba2e9246da3ec47102f79b9c2725ed155b4cf