[compiler-rt] [RISCV][compiler-rt] Small fixes for __riscv_feature_bits (PR #99958)

[Philip Reames via llvm-commits]

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@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "cpu_model.h"
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preames wrote:

I also prefer option 1.  @BeMg Can you take over this review?  I don't have a workable build environment for compiler-rt at the moment.  If you're happy with this change, feel free to take it, apply the change needed for it to build (option 1) and land.  

 I'm in the process of doing a native build of the 19.x release branch (including compiler-rt), but that's likely going to be another ~36 hours or so before it's complete and I can use it for incremental patch testing.

https://github.com/llvm/llvm-project/pull/99958