[PATCH] OvmfPkg/X86QemuLoadImageLib: fix "unused variable" error in X64 DXE builds

["Laszlo Ersek" <lersek@redhat.com>]

When the MDE_CPU_IA32 macro is not defined, there is no access to the
"KernelImageHandle" local variable in QemuStartKernelImage(). This breaks
the OvmfPkgIa32X64 and OvmfPkgX64 platform builds, at least with gcc-8.

Move the local variable to the inner scope, where declaration and usage
are inseparable.

(Note that such inner-scope declarations are frowned upon in the wider
edk2 codebase, but we use them liberally in ArmVirtPkg and OvmfPkg anyway,
because they help us reason about variable lifetime and visibility.)

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Fixes: 7c47d89003a6f8f7f6f0ce8ca7d3e87c630d14cc
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2572
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
    Ard, if you get to it first, feel free to push this in my stead. Thanks!
    
    Repo:   https://pagure.io/lersek/edk2.git
    Branch: x86qlil_build_fix

 OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.c b/OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.c
index c5bd6862b265..1868c9fcafdf 100644
--- a/OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.c
+++ b/OvmfPkg/Library/X86QemuLoadImageLib/X86QemuLoadImageLib.c
@@ -457,67 +457,68 @@ EFIAPI
 QemuStartKernelImage (
   IN  OUT EFI_HANDLE            *ImageHandle
   )
 {
   EFI_STATUS                    Status;
   OVMF_LOADED_X86_LINUX_KERNEL  *LoadedImage;
-  EFI_HANDLE                    KernelImageHandle;
 
   Status = gBS->OpenProtocol (
                   *ImageHandle,
                   &gOvmfLoadedX86LinuxKernelProtocolGuid,
                   (VOID **)&LoadedImage,
                   gImageHandle,                  // AgentHandle
                   NULL,                          // ControllerHandle
                   EFI_OPEN_PROTOCOL_GET_PROTOCOL
                   );
   if (!EFI_ERROR (Status)) {
     return QemuStartLegacyImage (*ImageHandle);
   }
 
   Status = gBS->StartImage (
                   *ImageHandle,
                   NULL,              // ExitDataSize
                   NULL               // ExitData
                   );
 #ifdef MDE_CPU_IA32
   if (Status == EFI_UNSUPPORTED) {
+    EFI_HANDLE KernelImageHandle;
+
     //
     // On IA32, EFI_UNSUPPORTED means that the image's machine type is X64 while
     // we are expecting a IA32 one, and the StartImage () boot service is unable
     // to handle it, either because the image does not have the special .compat
     // PE/COFF section that Linux specifies for mixed mode capable images, or
     // because we are running without the support code for that. So load the
     // image again, using the legacy loader, and unload the normally loaded
     // image before starting the legacy one.
     //
     Status = QemuLoadLegacyImage (&KernelImageHandle);
     if (EFI_ERROR (Status)) {
       //
       // Note: no change to (*ImageHandle), the caller will release it.
       //
       return Status;
     }
     //
     // Swap in the legacy-loaded image.
     //
     QemuUnloadKernelImage (*ImageHandle);
     *ImageHandle = KernelImageHandle;
     return QemuStartLegacyImage (KernelImageHandle);
   }
 #endif
   return Status;
 }
 
 /**
   Unloads an image loaded with QemuLoadKernelImage ().
 
   @param  ImageHandle             Handle that identifies the image to be
                                   unloaded.
 
   @retval EFI_SUCCESS             The image has been unloaded.
   @retval EFI_UNSUPPORTED         The image has been started, and does not
                                   support unload.
   @retval EFI_INVALID_PARAMETER   ImageHandle is not a valid image handle.
 
   @return                         Exit code from the image's unload function.
 **/
-- 
2.19.1.3.g30247aa5d201