Remove the -mrelax-all options passed onto the integrated assembler in -O0.
The -mrelax-all option causes short jumps emitted when lowering to be widened unconditionally. For cases where we need control of the length of the jump instruction (i.e. to make the jump instructions short) when lowering, -mrelax-all causes them all to be lengthened instead of relying on the instruction layout algorithms to make the decision appropriately.