Bug#1117654: OMP not built anymore on riscv64

[Matthias Klose <doko@debian.org>]

Package: src:llvm-toolchain-21
Version: 1:21.1.2-4
Severity: important
Tags: sid forky
X-Debbugs-CC: debian-riscv@lists.debian.org

llvm-defaults and 19 has support for OMP, but that is not available in 
the 21 package, while it looks to be supported upstream.  That will 
introduce a regression when making 21 the default.