Add one additional file to libllvmminimal, since in some cases (e.g.

upgrading from stable/10 to stable/11) symbols from it are needed to
link llvm-tblgen and clang-tblgen.

Reported by:	kib
MFC after:	3 days

lib/clang/libllvmminimal/Makefile

@@ -18,6 +18,7 @@ SRCS+=		Support/Errno.cpp
 SRCS+=		Support/Error.cpp
 SRCS+=		Support/ErrorHandling.cpp
 SRCS+=		Support/FoldingSet.cpp
+SRCS+=		Support/FormatVariadic.cpp
 SRCS+=		Support/FormattedStream.cpp
 SRCS+=		Support/Hashing.cpp
 SRCS+=		Support/Host.cpp