binutils/elf2flt: use alternate mirror

The official elf2flt upstream has disapeared.

Switch to a mirror.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 # windows config options

 ## depends on ARCH_x86

 ##

 ## select WINDOWS

 ##

 ## help Build a toolchain targeting systems running Windows as host