generalize sh entry point asm not to assume call dests fit in 12 bits
generalize sh entry point asm not to assume call dests fit in 12 bits

this assumption is borderline-unsafe to begin with, and fails badly
with -ffunction-sections since the linker can move the callee
arbitrarily far away when it lies in a different section.

chardi/musl,chardi/musl,chardi/musl