Disable PGO on RHEL

We don't want to enable this on RHEL until LLVM 21.

Author: tstellar

llvm.spec

@@ -98,7 +98,7 @@
 %ifarch %{ix86}
 %bcond_with pgo
 %else
-%if 0%{?fedora} >= 43 || 0%{?rhel} >= 9
+%if 0%{?fedora} >= 43 || (0%{?rhel} >= 9 && %{maj_ver} >= 21)
 %bcond_without pgo
 %else
 %bcond_with pgo