Revert "Make Directory::Current() work with unenhanced POSIX getcwd"

runtime/bin/directory_posix.cc

Index: runtime/bin/directory_posix.cc
diff --git a/runtime/bin/directory_posix.cc b/runtime/bin/directory_posix.cc
index df87bd639de288da8e4ce4fc8287d021ca8edb53..7adb80f9156ab2d308131aee2181243b35b85a27 100644
--- a/runtime/bin/directory_posix.cc
+++ b/runtime/bin/directory_posix.cc
@@ -376,30 +376,7 @@ Directory::ExistsResult Directory::Exists(const char* dir_name) {
 
 
 char* Directory::Current() {
-#if defined(TARGET_OS_LINUX) || defined(TARGET_OS_MACOS)
-
-  // On targets that support it, let getcwd allocate the buffer
-  // dynamically. (Not part of POSIX, but implemented on many platforms.)
   return getcwd(NULL, 0);
-
-#else
-
-  // POSIX getcwd requires a pre-allocated buffer.
-  char buffer[PATH_MAX];
-  if (NULL == getcwd(buffer, PATH_MAX)) {
-    return NULL;
-  }
-
-  size_t length = strlen(buffer) + 1;
-  char* result = reinterpret_cast<char*>(malloc(length));
-  if (result == NULL) {
-    return NULL;
-  }
-
-  strncpy(result, buffer, length);
-  return result;
-
-#endif
 }