Build failure on Mavericks

I am unable to build my project on Mavericks. I have a MacBook Pro with OS X 10.9.5(13F34).

I am hitting this error. fatal error: 'assert.h' file not found

I already searched the net & saw many people hitting this issue. The solution for this issue is to try "xcode-select --install" & then build. Unfortunately, this solution is not working for me. Every time I try this, I end up downloading the Command Line Tools (OS X 10.9) Version 6.0 & 6.1 but the subsequent build fails with the same problem as earlier.

I have already downloaded the Command Line Tools several times.

I have added a screen shot of my App Store which shows that I have downloaded Command Line Tools Version 6.0 & 6.1 several times today.

Any help, regarding this issue would be highly appreciated.

Thanks. Ganesh