[LTO] Ignore unreachable virtual functions in WPD in hybrid LTO.

Differential Revision: https://reviews.llvm.org/D115492

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -1066,6 +1066,7 @@ static uint64_t getEncodedFFlags(FunctionSummary::FFlags Flags) {
   RawFlags |= (Flags.NoUnwind << 6);
   RawFlags |= (Flags.MayThrow << 7);
   RawFlags |= (Flags.HasUnknownCall << 8);
+  RawFlags |= (Flags.MustBeUnreachable << 9);
   return RawFlags;
 }