We should not include both linux/prctl.h and sys/prctl.h. This works
with glibc because the latter includes the former, but breaks with musl
because the latter redeclares the contents of the former, resulting in:
```
/usr/local/aarch64-linux-musl/include/sys/prctl.h:88:8: error:
redefinition of 'struct prctl_mm_map'
88 | struct prctl_mm_map {
| ^~~~~~~~~~~~
In file included from
/checkout/src/llvm-project/llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp:13:
/usr/local/aarch64-linux-musl/include/linux/prctl.h:134:8: note:
previous definition of 'struct prctl_mm_map'
134 | struct prctl_mm_map {
| ^~~~~~~~~~~~
```
Fixes https://github.com/llvm/llvm-project/issues/139443.
a2c0ac06ff