OvmfPkg/OvmfXen: Build platform info HOB in XenPlatformPei

Copy the function BuildPlatformInfoHob() from OvmfPkg/PlatformPei.

QemuFwCfgLib expect this HOB to be present, or fails to do anything.
InternalQemuFwCfgIsAvailable() from QemuFwCfgPeiLib module will not
check if the HOB is actually present for example and try to use a NULL
pointer.

Fixes: cda98df162 ("OvmfPkg/QemuFwCfgLib: remove mQemuFwCfgSupported + mQemuFwCfgDmaSupported")
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Jiewen Yao <jiewen.yao@intel.com>

OvmfPkg/XenPlatformPei/Platform.c

@@ -17,6 +17,7 @@
 //
 // The Library classes this module consumes
 //
+#include <Library/BaseMemoryLib.h>
 #include <Library/BaseLib.h>
 #include <Library/DebugLib.h>
 #include <Library/HobLib.h>
@@ -409,6 +410,20 @@ DebugDumpCmos (
   }
 }
 
+EFI_HOB_PLATFORM_INFO *
+BuildPlatformInfoHob (
+  VOID
+  )
+{
+  EFI_HOB_PLATFORM_INFO  PlatformInfoHob;
+  EFI_HOB_GUID_TYPE      *GuidHob;
+
+  ZeroMem (&PlatformInfoHob, sizeof PlatformInfoHob);
+  BuildGuidDataHob (&gUefiOvmfPkgPlatformInfoGuid, &PlatformInfoHob, sizeof (EFI_HOB_PLATFORM_INFO));
+  GuidHob = GetFirstGuidHob (&gUefiOvmfPkgPlatformInfoGuid);
+  return (EFI_HOB_PLATFORM_INFO *)GET_GUID_HOB_DATA (GuidHob);
+}
+
 /**
   Perform Platform PEI initialization.
 
@@ -429,6 +444,11 @@ InitializeXenPlatform (
 
   DEBUG ((DEBUG_INFO, "Platform PEIM Loaded\n"));
 
+  //
+  // Platform Info HOB used by QemuFw libraries
+  //
+  BuildPlatformInfoHob ();
+
   DebugDumpCmos ();
 
   if (!XenDetect ()) {

OvmfPkg/XenPlatformPei/Platform.h

@@ -12,6 +12,7 @@
 #define _PLATFORM_PEI_H_INCLUDED_
 
 #include <IndustryStandard/E820.h>
+#include <Library/PlatformInitLib.h>
 
 VOID
 AddIoMemoryBaseSizeHob (