Sometime back I saw this email thread [1] where it was specified that in Arduino 1.0, we will have support for per sketch cflags directives.
Was that implemented in Arduino 1.0? I couldn't find any reference in the release notes [2]
[1] - http://arduino.cc/pipermail/developers_arduino.cc/2011-July/005208.html
[2] - http://arduino.cc/en/Main/ReleaseNotes