Stop using precompiled headers for Linux?

[Ioi Lam]

Is there any advantage of using precompiled headers on Linux? It's on by 
default and we keep having breakage where someone would forget to add 
#include. The latest instance is JDK-8213148.

I just turn on precompiled headers explicitly in all my builds. I don't 
see any difference in build time (at least not significant enough for me 
to bother).

Should we disable it by default on Linux?

Thanks

- Ioi