Hi,

When build ovmf with the latest two commits of master branch, we meet error on Red Hat 7.6 with gcc version 4.8.5, but succeed on Red Hat 8.0 with gcc version 8.2.1.

Steps:
git clone https://github.com/tianocore/edk2.git
cd edk2
git submodule init
git submodule update -recursive
OvmfPkg/build.sh -a X64 -n 64

Error log:
.......
/home/build/kvm_build/nightly/kvm_qemu/kvm-next-20190813010558-a738b5e7-5e7bcdcf/edk2/MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c:641:50: error: 'PageMapLevel5Entry' may be used uninitialized in this function [-Werror=maybe-uninitialized]
   PAGE_MAP_AND_DIRECTORY_POINTER                *PageMapLevel5Entry;
                                                  ^
cc1: all warnings being treated as errors
"objcopy"  /home/build/kvm_build/nightly/kvm_qemu/kvm-next-20190813010558-a738b5e7-5e7bcdcf/edk2/Build/OvmfX64/DEBUG_GCC48/X64/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciHostBridgeDxe/DEBUG/PciHostBridgeDxe.dll
"GenFw" -e UEFI_DRIVER -o /home/build/kvm_build/nightly/kvm_qemu/kvm-next-20190813010558-a738b5e7-5e7bcdcf/edk2/Build/OvmfX64/DEBUG_GCC48/X64/OvmfPkg/XenBusDxe/XenBusDxe/OUTPUT/XenBusDxe.efi /home/build/kvm_build/nightly/kvm_qemu/kvm-next-20190813010558-a738b5e7-5e7bcdcf/edk2/Build/OvmfX64/DEBUG_GCC48/X64/OvmfPkg/XenBusDxe/XenBusDxe/DEBUG/XenBusDxe.dll
make: *** [/home/build/kvm_build/nightly/kvm_qemu/kvm-next-20190813010558-a738b5e7-5e7bcdcf/edk2/Build/OvmfX64/DEBUG_GCC48/X64/MdeModulePkg/Core/DxeIplPeim/DxeIpl/OUTPUT/X64/VirtualMemory.obj] Error 1
cp -f /home/build/kvm_build/nightly/kvm_qemu/kvm-next-20190813010558-a738b5e7-5e7bcdcf/edk2/Build/OvmfX64/DEBUG_GCC48/X64/OvmfPkg/XenBusDxe/XenBusDxe/OUTPUT/XenBusDxe.efi /home/build/kvm_build/nightly/kvm_qemu/kvm-next-20190813010558-a738b5e7-5e7bcdcf/edk2/Build/OvmfX64/DEBUG_GCC48/X64/OvmfPkg/XenBusDxe/XenBusDxe/DEBUG


build.py...
: error 7000: Failed to execute command
        make tbuild [/home/build/kvm_build/nightly/kvm_qemu/kvm-next-20190813010558-a738b5e7-5e7bcdcf/edk2/Build/OvmfX64/DEBUG_GCC48/X64/MdeModulePkg/Core/DxeIplPeim/DxeIpl]




build.py...
: error F002: Failed to build module
        /home/build/kvm_build/nightly/kvm_qemu/kvm-next-20190813010558-a738b5e7-5e7bcdcf/edk2/MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf [X64, GCC48, DEBUG]

- Failed -
Build end time: 08:46:33, Aug.13 2019
Build total time: 00:01:15

GCC:
gcc --version
gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-36)
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.


Thanks,
Fan