[U-Boot] what are RELFLAGS?

We seem to set CPPFLAGS to include RELFLAGS but I'm wondering how PLATFORM_ RELFLAGS is suppose to differ from PLATFORM_CPPFLAGS.

I especially love the following:

cpu/i386/config.mk:PLATFORM_RELFLAGS += cpu/nios/config.mk:PLATFORM_RELFLAGS += cpu/nios2/config.mk:PLATFORM_RELFLAGS +=

(Yes they are blank after the +=)

- k