Support Windows builds for libartbase/libdexfile

Enable building key libraries for windows tools in the SDK.

Bug: 22322814
Test: run dexdumps on a large APK under wine on Linux
Change-Id: Ib7180f8385300244bf914e9ae1f993e869f71109
diff --git a/libdexfile/dex/dex_file_loader.cc b/libdexfile/dex/dex_file_loader.cc
index 1884bcf..a719d41 100644
--- a/libdexfile/dex/dex_file_loader.cc
+++ b/libdexfile/dex/dex_file_loader.cc
@@ -187,12 +187,18 @@
   std::string base_location = GetBaseLocation(dex_location);
   const char* suffix = dex_location + base_location.size();
   DCHECK(suffix[0] == 0 || suffix[0] == kMultiDexSeparator);
+#ifdef _WIN32
+  // Warning: No symbolic link processing here.
+  PLOG(WARNING) << "realpath is unsupported on Windows.";
+#else
   // Warning: Bionic implementation of realpath() allocates > 12KB on the stack.
   // Do not run this code on a small stack, e.g. in signal handler.
   UniqueCPtr<const char[]> path(realpath(base_location.c_str(), nullptr));
   if (path != nullptr && path.get() != base_location) {
     return std::string(path.get()) + suffix;
-  } else if (suffix[0] == 0) {
+  }
+#endif
+  if (suffix[0] == 0) {
     return base_location;
   } else {
     return dex_location;