linux-libre-firmware 1.4 fails to build on Arch Linux

[Dimitri Kaparis]

Greetings,
Trying to build linux-libre-firmware 1.4 package from https://jxself.org/firmware/ on current Arch Linux system gives me the following error:

```
...
make[1]: Entering directory '/.../linux-libre-firmware-1.4/src/atusb'
  CC        atusb.o
  CC        board.o
In file included from board.c:26:
board.c: In function 'panic':
board.h:32:33: error: array subscript 0 is outside array bounds of 'volatile uint8_t[0]' {aka 'volatile unsigned char[]'} [-Werror=array-bounds]
   32 | #define CLR_2(p, b)     PORT##p &= ~(1 << (b))
      |                                 ^~
board.h:38:25: note: in expansion of macro 'CLR_2'
   38 | #define CLR_1(p, b)     CLR_2(p, b)
      |                         ^~~~~
board.h:44:25: note: in expansion of macro 'CLR_1'
   44 | #define CLR(n)          CLR_1(n##_PORT, n##_BIT)
      |                         ^~~~~
board.c:98:17: note: in expansion of macro 'CLR'
   98 |                 CLR(LED);
      |                 ^~~
cc1: all warnings being treated as errors
make[1]: *** [Makefile:165: board.o] Error 1
make[1]: Leaving directory '/.../linux-libre-firmware-1.4/src/atusb'
make: *** [Makefile:40: atusb] Error 2
==> ERROR: A failure occurred in build().
    Aborting...
```

Any advice?

Thanks,
Dimitri