I read carefully that page several times before asking my question.
unfortunately build-flags apply to ALL the environment.
my question was if is there a way to specify different sets of flags for different group of files in the same build environment and not for different target environment.
may be I want to specify different include search path for different group of source files to avoid filename conflicts if i am going to integrate some libraries, or i need to specify a log related define (es. -DLOG_DEBUG) only for a specific source....
second question is unfortunately unanswered
thank you anyway