I wrote an ebuild for a software that uses SCons as its build system. My 
guide was scons-utils.eclass and some other ebuilds that were using it. 
It pretty much boils down to:

   src_compile()
   {
	tc-export CC CXX
	append-cflags -Wno-error
	append-cxxflags -Wno-error
	escons PREFIX=/usr DESTDIR="${D}" || die
   }

   src_install()
   {
	escons PREFIX=/usr DESTDIR="${D}" install || die
   }

But it ignores the CFLAGS/CXXFLAGS/LDFLAGS set in make.conf, and 
append-cflags and append-cxxflags does nothing (-Wno-error is not used 
in the resulting build.)

I'm not sure where to go from here.