[mini helpers] strip more directives on arm (#11124)

[mini helpers] strip more directives on arm (#11124)

* `-s` removes all symbols.
* `-x` removes non-global symbols.

This is needed in order to get human readable output with `MONO_VERBOSE_METHOD=method`, so instead of:

```
Disassembly of section .text:

00000000 <.text>:
   0:   e92d4900        .word   0xe92d4900
   4:   e24dd05c        .word   0xe24dd05c
   8:   e1a0b00d        .word   0xe1a0b00d
   c:   e58b0030        .word   0xe58b0030
  10:   e58b1034        .word   0xe58b1034
[...]
```

It is this now:
```
Disassembly of section .text:

00000000 <.text>:
   0:   e92d4900        push    {r8, fp, lr}
   4:   e24dd05c        sub     sp, sp, #92     ; 0x5c
   8:   e1a0b00d        mov     fp, sp
   c:   e58b0030        str     r0, [fp, #48]   ; 0x30
  10:   e58b1034        str     r1, [fp, #52]   ; 0x34
[...]
```

This is needed due to a newer toolchain on our ARM bots. Tested on armv7 and aarch64.