Bug#1082284: libunwind: FTBFS on arm64: expected 'unw_tdep_context_t *' but argument is of type 'ucontext_t *'

[Simon McVittie <smcv@debian.org>]

Source: libunwind
Version: 1.7.2-1
Severity: serious
Tags: ftbfs
Justification: fails to build from source (but built successfully in the past)
User: debian-arm@lists.debian.org
Usertags: arm64
X-Debbugs-Cc: debian-arm@lists.debian.org

Vaguely similar to the i386 build failure in the same version that I
reported separately:

https://buildd.debian.org/status/fetch.php?pkg=libunwind&arch=arm64&ver=1.7.2-1&stamp=1726720968&raw=0
> In file included from aarch64/Linit.c:4:
> aarch64/Ginit.c: In function 'access_reg':
> aarch64/Ginit.c:373:28: error: initialization of 'unw_tdep_context_t *' from incompatible pointer type 'ucontext_t *' [-Wincompatible-pointer-types]
>   373 |   unw_tdep_context_t *uc = ((struct cursor *)arg)->uc;
>       |                            ^
> aarch64/Ginit.c: In function 'access_fpreg':
> aarch64/Ginit.c:402:28: error: initialization of 'unw_tdep_context_t *' from incompatible pointer type 'ucontext_t *' [-Wincompatible-pointer-types]
>   402 |   unw_tdep_context_t *uc = ((struct cursor *)arg)->uc;
>       |                            ^

(There are many more errors involving `unw_tdep_context_t *` and
`ucontext_t *` not being interchangeable, I only quoted the first
two here.)

Thanks,
    smcv