[CMake] How to switch off dependencies in special cases?

[Jorrit Schaap]

Hi,

I'm using cmake on linux with gcc.
The dependencies feature of cmake is realy great, but sometimes I would like
to switch it of. A complete build of all our libs takes a couple of ours. 

Whenever I add for example a comment to a top level header file (which is
include direct or indirect by many cpp files) this triggers a very long
build, even though no actual code changed in the header, and hence no long
build is needed. I know you can reduce dependencies by using a lot of forward
declarations etc, but that's not the point. 

Is it possible to tell cmake to igore the changed timestamp of a particular
file when it scans for dependencies?

Thanks, 
Jorrit