[libFuzzer] Encapsulate commands in a class.

Summary:
To be more portable (especially w.r.t. platforms without system()),
commands should be managed programmatically rather than via string
manipulation on the command line. This change introduces
Fuzzer::Command, with methods to manage arguments and flags, set output
options, and execute the command.

Patch By: aarongreen

Reviewers: kcc, morehouse

Reviewed By: kcc, morehouse

Subscribers: llvm-commits, mgorny

Differential Revision: https://reviews.llvm.org/D40103

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk/lib/fuzzer@319680 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/FuzzerUtilWindows.cpp b/FuzzerUtilWindows.cpp
index e8bdd2e..8227e77 100644
--- a/FuzzerUtilWindows.cpp
+++ b/FuzzerUtilWindows.cpp
@@ -10,6 +10,7 @@
 //===----------------------------------------------------------------------===//
 #include "FuzzerDefs.h"
 #if LIBFUZZER_WINDOWS
+#include "FuzzerCommand.h"
 #include "FuzzerIO.h"
 #include "FuzzerInternal.h"
 #include <cassert>
@@ -151,8 +152,9 @@
   return _popen(Command, Mode);
 }
 
-int ExecuteCommand(const std::string &Command) {
-  return system(Command.c_str());
+int ExecuteCommand(const Command &Cmd) {
+  std::string CmdLine = Cmd.toString();
+  return system(CmdLine.c_str());
 }
 
 const void *SearchMemory(const void *Data, size_t DataLen, const void *Patt,