Replace StringRef with std::string in LinkerDriver::addLibrary(StringRef Name) because std::string is destroyed after assigning what fills the buffer with garbage and StringRef is no more valid.
That fixes few failing tests under windows+msvs2015(debug).

llvm-svn: 259186
diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 7909336..2b0789b 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -114,7 +114,7 @@
 
 // Add a given library by searching it from input search paths.
 void LinkerDriver::addLibrary(StringRef Name) {
-  StringRef Path = searchLibrary(Name);
+  std::string Path = searchLibrary(Name);
   if (Path.empty())
     error("Unable to find library -l" + Name);
   else