[find-all-symbols] Save absolute file path instead of relative file path in SymbolInfo.

[bkramer]

lg.

[hokein]

Don't append absolute path to build directory.

We will get the absolute file paths in some cases, such as STL.

include-fixer/find-all-symbols/FindAllSymbols.cpp

 #include "SymbolInfo.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/Type.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include "clang/Tooling/Tooling.h"
 #include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Path.h"
 
 using namespace clang::ast_matchers;
 
 namespace clang {
 namespace find_all_symbols {
 namespace {
 void SetContext(const NamedDecl *ND, SymbolInfo *Symbol) {
   for (const auto *Context = ND->getDeclContext(); Context;
if (!Loc.isValid()) {
     llvm::errs() << "Declaration " << ND->getNameAsString() << "("
                  << ND->getDeclKindName()
                  << ") has invalid declaration location.";
     return false;
   }
   std::string FilePath = Result.SourceManager->getFilename(Loc).str();
   if (FilePath.empty())
     return false;
-
+  auto WorkingDir = Result.SourceManager->getFileManager()
+                        .getVirtualFileSystem()
+                        ->getCurrentWorkingDirectory();
+  if (WorkingDir) {
+    llvm::SmallString<128> AbsolutePath(*WorkingDir);
+    llvm::sys::path::append(AbsolutePath, FilePath);
+    llvm::sys::path::remove_dots(AbsolutePath, true);
+    Symbol->FilePath = AbsolutePath.str();
+  } else {
     Symbol->FilePath = FilePath;
+  }
+
   Symbol->LineNumber = Result.SourceManager->getExpansionLineNumber(Loc);
   return true;
 }
 } // namespace
 
 void FindAllSymbols::registerMatchers(MatchFinder *MatchFinder) {
   // FIXME: Handle specialization.
   auto IsInSpecialization = hasAncestor(