Description of problem:
Compilation fails on aarch64, reproducer with e.g. roc-toolkit.

Version-Release number of selected component (if applicable):
libunwind-devel-1.6.2-5.fc38

How reproducible:
Always

Steps to Reproduce:
1. fedpkg co roc-toolkit
2. drop excludearch for aarch64
3. fedpkg scratch-build --srpm --arches aarch64

Actual results:
In file included from /usr/include/libunwind.h:5,
                 from src/modules/roc_core/target_libunwind/roc_core/backtrace.cpp:10:
/usr/include/libunwind-aarch64.h:198:17: error: expected identifier before numeric constant
  198 |         alignas(16) uint8_t __reserved[(66 * 8)];
      |                 ^~
/usr/include/libunwind-aarch64.h:198:17: error: expected ‘,’ or ‘...’ before numeric constant
/usr/include/libunwind-aarch64.h:198:19: error: expected ‘;’ at end of member declaration
  198 |         alignas(16) uint8_t __reserved[(66 * 8)];
      |                   ^
      |                    ;


Expected results:
No error

Additional info:
It's probably related to this upstream commit:
https://github.com/libunwind/libunwind/pull/186/commits/e72fe5376e7084017d8f56ecdfea3d4766e5e3fb