[Driver] Use SmallVectorImpl reference instead of SmallVector reference in MultilibSet. NFC

We prefer to pass SmallVectorImpl reference so that no specific
inline size is required.

Author: topperc

clang/include/clang/Driver/Multilib.h

@@ -130,7 +130,7 @@ class MultilibSet {
 
   /// Select compatible variants, \returns false if none are compatible
   bool select(const Multilib::flags_list &Flags,
-              llvm::SmallVector<Multilib> &) const;
+              llvm::SmallVectorImpl<Multilib> &) const;
 
   unsigned size() const { return Multilibs.size(); }
 

clang/lib/Driver/Multilib.cpp

@@ -95,7 +95,7 @@ MultilibSet &MultilibSet::FilterOut(FilterCallback F) {
 void MultilibSet::push_back(const Multilib &M) { Multilibs.push_back(M); }
 
 bool MultilibSet::select(const Multilib::flags_list &Flags,
-                         llvm::SmallVector<Multilib> &Selected) const {
+                         llvm::SmallVectorImpl<Multilib> &Selected) const {
   llvm::StringSet<> FlagSet(expandFlags(Flags));
   Selected.clear();