win: Add a note about /Z7 obsolescence regarding CodeView debug info

compat/non_win/dbghelp.h

Index: compat/non_win/dbghelp.h
diff --git a/compat/non_win/dbghelp.h b/compat/non_win/dbghelp.h
index 08f07ae87c295ff6a68a98c1012119ad74672229..ecf8bab81844e326e13f14f67e007b5d73728927 100644
--- a/compat/non_win/dbghelp.h
+++ b/compat/non_win/dbghelp.h
@@ -564,7 +564,9 @@ struct __attribute__((packed, aligned(4))) MINIDUMP_MODULE {
   //! CodeView 4.1 format. Signatures seen in the wild include “NB09”
   //! (0x3930424e) for CodeView 4.1 and “NB11” (0x3131424e) for CodeView 5.0.
   //! This form of debugging information within the module, as opposed to a link
-  //! to an external `.pdb` file, is chosen by building with `/Z7`.
+  //! to an external `.pdb` file, is chosen by building with `/Z7` in Visual
+  //! Studio 6.0 (1998) and earlier. This embedded form of debugging information
+  //! is now considered obsolete.
   //!
   //! On Windows, the CodeView record is taken from a module’s
   //! IMAGE_DEBUG_DIRECTORY entry whose Type field has the value