3.6.12.3 Iquote Option
The -iquote dir option adds the
directory dir to the list of directories
to be searched for header files during preprocessing. Directories specified
with this option apply only to the quoted form of the directive, for example
#include "file", and the directory is searched only
after the current working directory has been searched. If this option is
used more than once, the directories they specify are searched in a
left-to-right order as they appear on the command line.