Build error with freebl: prtypes.h:556:38: error: size of array ‘arg’ is negative

[Paul Menzel]

Dear LibreOffice folks,


Building current master on Ubuntu 21.04 (ppc64le) fails:

```
$ gcc --version
gcc (Ubuntu 10.3.0-1ubuntu1) 10.3.0
[…]
$ git describe --dirty
libreoffice-7-2-branch-point-1293-g1738f106bd73
$ make
[…]
In file included from ../../../dist/out/include/prerror.h:9,
                  from drbg.c:9:
drbg.c: In function ‘RNG_RandomUpdate’:
../../../dist/out/include/prtypes.h:556:38: error: size of array ‘arg’ 
is negative
   556 |     extern void pr_static_assert(int arg[(condition) ? 1 : -1])
       |                                      ^~~
drbg.c:609:5: note: in expansion of macro ‘PR_STATIC_ASSERT’
   609 |     PR_STATIC_ASSERT(sizeof(size_t) <= 4);
       |     ^~~~~~~~~~~~~~~~
make[7]: *** [../../coreconf/rules.mk:279: 
out/Linux_SINGLE_SHLIB/drbg.o] Error 1
make[6]: *** [Makefile:680: freebl_FREEBL_BUILD_SINGLE_SHLIB] Error 2
make[5]: *** [../coreconf/rules.mk:37: freebl] Error 2
[…]
```


Kind regards,

Paul