StandaloneMmPkg: Avoid updating attributes on 0 length sections

PE images can have a zero virtual length section for placeholders, unused
relocation, or other artifacts. At best, updated attributes on such sections
is a no-op, but at worst is can cause spurious errors and asserts. Specifically
asserts have been observed in Hafnium when attempting to update attributes
on a zero length section. It is best to just skip such sections entirely.

This commit simply logs and skips these sections explicitly.

Signed-off-by: Chris Fernald <chfernal@microsoft.com>

StandaloneMmPkg/Library/StandaloneMmPeCoffExtraActionLib/AArch64/StandaloneMmPeCoffExtraActionLib.c

@@ -164,7 +164,15 @@ UpdatePeCoffPermissions (
 
     Base = TmpContext.ImageAddress + SectionHeader.VirtualAddress;
 
-    if ((SectionHeader.Characteristics & EFI_IMAGE_SCN_MEM_EXECUTE) == 0) {
+    if (SectionHeader.Misc.VirtualSize == 0) {
+      DEBUG ((
+        DEBUG_INFO,
+        "%a: Skipping section %d of image at 0x%lx with size 0\n",
+        __func__,
+        Index,
+        Base
+        ));
+    } else if ((SectionHeader.Characteristics & EFI_IMAGE_SCN_MEM_EXECUTE) == 0) {
       if ((SectionHeader.Characteristics & EFI_IMAGE_SCN_MEM_WRITE) == 0) {
         DEBUG ((
           DEBUG_INFO,