[clang] Use cmake to find perl executable (PR #91275)

[Jon Roelofs via cfe-commits]

================
@@ -1,4 +1,4 @@
-REQUIRES: shell
+REQUIRES: perl
----------------
jroelofs wrote:

should be:
```
REQUIRES: perl, shell
```

right?

https://github.com/llvm/llvm-project/pull/91275