OvmfPkg: Fix SMM/RT driver section alignment for XCODE5/CLANGPDB

OvmfPkg: Fix SMM/RT driver section alignment for XCODE5/CLANGPDB

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2642

This patch resolves the problem of using memory protection
attributes when OVMF firmware is compiled with XCODE5 and CLANGPDB.

Cc: Andrew Fish <afish@apple.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Marvin Häuser <mhaeuser@outlook.de>
Signed-off-by: Vitaly Cheptsov <vit9696@protonmail.com>
Message-Id: <20200329132158.35259-2-cheptsov@ispras.ru>
Acked-by: Laszlo Ersek <lersek@redhat.com>
[lersek@redhat.com: fix whitespace issues reported by git-am]
[lersek@redhat.com: replace "CC:" tags with "Cc:" ones for PatchCheck.py]