[Bug libitm/124237] New: aarch64: libitm is not marked with GCS when built with -mbranch-protection=standard

[ykhrustalev at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124237

            Bug ID: 124237
           Summary: aarch64: libitm is not marked with GCS when built with
                    -mbranch-protection=standard
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: libitm
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ykhrustalev at gcc dot gnu.org
  Target Milestone: ---

When "-mbranch-protection=standard" is enabled for target libraries, libitm is
not marked with GCS. Both BTI and PAC markings are present, but GCS is not:

```
$ readelf -n lib64/libitm.so

      Properties: AArch64 feature: BTI, PAC

```

Compare with libatomic:

```
$ readelf -n lib64/libatomic.so

      Properties: AArch64 feature: BTI, PAC, GCS
```

This can be fixed by adding a relevant GCS property to
libitm/config/aarch64/sjlj.S.