arm64: don't interpret DW_CFA_GNU_window_save

DW_CFA_AARCH64_negate_ra_state uses the same encoding as
DW_CFA_GNU_window_save. It is meant to indicate that x30/LR
has been signed, but breakpad does not require this information.

Bug: b/239086293
Change-Id: I5a17bd5e0673a3ff80a8c6e347013d66054314e8
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/3781136
Reviewed-by: Mark Mentovai <mark@chromium.org>

src/common/dwarf_cfi_to_module.h

@@ -152,6 +152,8 @@ class DwarfCFIToModule: public CallFrameInfo::Handler {
                                  const string& expression);
   virtual bool End();
 
+  virtual string Architecture();
+
  private:
   // Return the name to use for register REG.
   string RegisterName(int i);