Set blank CFLAGS/CPPFLAGS and then append user CFLAGS/CPPFLAGS. This allows us to pass them to the configure tests and keep our sed to extract them portable.
Set blank CFLAGS/CPPFLAGS and then append user CFLAGS/CPPFLAGS.
This allows us to pass them to the configure tests and keep our
sed to extract them portable.

rsmarples/dhcpcd,rsmarples/dhcpcd,rsmarples/dhcpcd