[CMake] -D getting stripped from some C Flags

[Poor Yorick]

while building plplot-5.95 with cmake-2.8.0, I got this error:

bin/g++ -m32 -Dplplotwxwidgetsd_EXPORTS -DHAVE_CONFIG_H -fPIC
-I/path/to/src/plplot-5.9.5/plplot-5.9.5/include
-I/path/to/src/plplot-5.9.5/plplot-5.9.5/lib/qsastime
-I/path/to/src/plplot-5.9.5/plplot-5.9.5/bindings/c++
-I/path/to/src/plplot-5.9.5/plplot-5.9.5
-I/path/to/src/plplot-5.9.5/plplot-5.9.5/bindings/wxwidgets
-I/path/to/wxPython-src-2.8.9.2/lib/wx/include/gtk2-unicode-release-2.8
-I/path/to/wxPython-src-2.8.9.2/include/wx-2.8
_FILE_OFFSET_BITS=64 _LARGE_FILES _LARGEFILE_SOURCE=1 __WXGTK__
-DUSINGDLL -o CMakeFiles/plplotwxwidgetsd.dir/wxPLplotstream.cpp.o
-c
/path/to/src/plplot-5.9.5/plplot-5.9.5/bindings/wxwidgets/wxPLplotstream.cpp

g++: _FILE_OFFSET_BITS=64: No such file or directory 

It looks like the "-D" got eaten.  Someone else had the same problem:

http://bbs.archlinux.org/viewtopic.php?id=85839

Is this a cmake bug?  If so, any patches I can apply to remove it?

-- 
Yorick