[MachO] Fix struct size assertion

std::vector can have different sizes depending on the STL's debug level,
so account for its size separately. (You could argue that we should be
accounting for all the other members separately as well, but that would
be very unergonomic, and std::vector is the only one that's caused
problems so far.)

Author: smeenai

lld/MachO/InputSection.cpp

@@ -26,8 +26,11 @@ using namespace llvm::support;
 using namespace lld;
 using namespace lld::macho;
 
-// Verify ConcatInputSection's size on 64-bit builds.
-static_assert(sizeof(void *) != 8 || sizeof(ConcatInputSection) == 120,
+// Verify ConcatInputSection's size on 64-bit builds. The size of std::vector
+// can differ based on STL debug levels (e.g. iterator debugging on MSVC's STL),
+// so account for that.
+static_assert(sizeof(void *) != 8 ||
+                  sizeof(ConcatInputSection) == sizeof(std::vector<Reloc>) + 96,
               "Try to minimize ConcatInputSection's size, we create many "
               "instances of it");