[Bug pch/47430] [4.6 Regression] Random PCH related bootstrap failures on powerpc64-linux

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47430

--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-01-25 
11:07:04 UTC ---
2) make sure other PCH is not read during compilation that is writing PCH

makes sense to me anyway