pthread.h not compiling with CrossWorks Linux version

I have a simple main.c that includes pthread.h which is located in /usr/include (I did an #apt-get install build-essential) to populate /usr/include
I can build the main (#gcc -o output_file main.c) and run the ./output_file which has a printf "Hello World").

For CrossWorks, I added /usr/include to Project/Properties and Code/Preprocessor and then System Include Directories

That seemed to satisfy the pthread.h not found error I was getting but I am not sure it is the correct place to add /usr/include
I try to build the same main.c in CrossWorks and I get errors in header files such as cpu-set.h and sched.h etc where extern declarations are made.

Thanks for any help

Richard Sideleau (rsideleau@yahoo.com)