Partial parallel build of several subtargets fails

_From [euge...@google.com](https://code.google.com/u/101600367715055138223/) on December 29, 2012 05:02:46_

mkdir build
cd build
cmake ..
make drsyscall drutil drmgr drpreload -j35

Results in pages of errors in generated headers under build/dynamorio/cmake/../include

Taking a closer look at the headers, them seems like they were written concurrently from several processes: they've got multiline comments mixed with unrelated code (which goes right inside the comment), and, for example, dr_ir_macros.h ends with the header guard repeated 3 times:

#endif /\* _DR_IR_MACROS_H_ */

#endif /\* _DR_IR_MACROS_H_ */

#endif /\* _DR_IR_MACROS_H_ */

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=1107_