Bug 1481005 - Explicitly delete dtor of AlignmentFinder::Alinger to avoid MSVC warning breaking debug builds. r=froydnj

Bug 1480624 added new code that results in a warning on MSVC debug builds. This
warning is treated as an error and makes such builds unhappy. The warning is
due to implicit deletion of a dtor, this changeset makes that deletion
explicit to avoid the fatal warning.

Differential Revision: https://phabricator.services.mozilla.com/D2865

--HG--
extra : moz-landing-system : lando

mfbt/Alignment.h

@@ -26,6 +26,12 @@ class AlignmentFinder
   {
     char mChar;
     T mT;
+
+    // Aligner may be used to check alignment of types with deleted dtors. This
+    // results in such specializations having implicitly deleted dtors, which
+    // causes fatal warnings on MSVC (see bug 1481005). As we don't create
+    // Aligners, we can avoid this warning by explicitly deleting the dtor.
+    ~Aligner() = delete;
   };
 
 public: