You're using the gp32_sdk.specs file, right?
in the gp32_sdk.ld file, found in /path/to/devkitARM/arm-elf/lib, add *(.bss*)
to the .bss section after *(COMMON)
.bss ALIGN(4) :
{
__bss_start = ABSOLUTE(.);
/* __bss_start__ = ABSOLUTE(.); */
*(.dynbss)
*(.gnu.linkonce.b*)...