Nowadays, the code fetching command line options via semi-hosting are
unconditionally pulled in, so that the semi-hosting code is still
there even I compile with option --specs=nosys.specs.
gdb ./aarch64-none-elf/libgloss/aarch64/crt0.o
(gdb) disassemble _start
0x0000000000000050 <+80>: ldr x1, 0x128 <_cpu_init_hook+48>
0x0000000000000054 <+84>: mov w0, #0x15
0x0000000000000058 <+88>: hlt #0xf000
This patch fixes this problem by wrapping the code by ARM_RDI_MONITOR.
When semi-hosting is not used, set command line options to NULL.
32ca315312