wpkg --cflags

Options Comments
--admindir Define the administration directory, where the database of the installed packages resides.
--debug Define a set of flags of things to print out for debug purposes.
--instdir Define the installation directory, where the data files are installed on the target.
--quiet Not used.
--root Define the installation root path.
--verbose Not used.

The --cflags command comes from pkg-config. It returns the list of options to use on a C/C++ command line to compile with the specified package.

wpkg --cflags wpkg
-I/usr/include/wpkg -I/usr/include

The pkg-config support in wpkg also includes --libs which is used to list options when linking object files with the specified package.