[dsymutil] Re-enable 'auto' verification as the default

This patch re-enabled auto as the default verification mode when
building with assertions or expensive checks. This was disabled in
c2d2f72 because of an issue with temp files on Windows, which was
fixed in 519490f26260.

(cherry picked from commit c296c35)

Author: JDevlieghere

llvm/tools/dsymutil/dsymutil.cpp

@@ -91,7 +91,7 @@ enum class DWARFVerify : uint8_t {
   All = Input | Output,
   Auto = Input | OutputOnValidInput,
 #if !defined(NDEBUG) || defined(EXPENSIVE_CHECKS)
-  Default = None // FIXME: Auto
+  Default = Auto
 #else
   Default = None
 #endif