[BOLT] Use SmallString::operator std::string (NFC)

Author: kazutakahirata

bolt/tools/bat-dump/bat-dump.cpp

@@ -75,7 +75,7 @@ static std::string GetExecutablePath(const char *Argv0) {
     if (llvm::ErrorOr<std::string> P =
             llvm::sys::findProgramByName(ExecutablePath))
       ExecutablePath = *P;
-  return std::string(ExecutablePath.str());
+  return std::string(ExecutablePath);
 }
 
 void dumpBATFor(llvm::object::ELFObjectFileBase *InputFile) {

bolt/tools/driver/llvm-bolt.cpp

@@ -174,7 +174,7 @@ static std::string GetExecutablePath(const char *Argv0) {
     if (llvm::ErrorOr<std::string> P =
             llvm::sys::findProgramByName(ExecutablePath))
       ExecutablePath = *P;
-  return std::string(ExecutablePath.str());
+  return std::string(ExecutablePath);
 }
 
 int main(int argc, char **argv) {

bolt/tools/heatmap/heatmap.cpp

@@ -46,7 +46,7 @@ static std::string GetExecutablePath(const char *Argv0) {
     if (llvm::ErrorOr<std::string> P =
             llvm::sys::findProgramByName(ExecutablePath))
       ExecutablePath = *P;
-  return std::string(ExecutablePath.str());
+  return std::string(ExecutablePath);
 }
 
 int main(int argc, char **argv) {