EmulatorPkg: Make the shell be the first boot option

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=1649

Make the shell be the first boot option by default,
So it can boot into UEFI Internal Shell directly

Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Andrew Fish <afish@apple.com>
Cc: Ray Ni <ray.ni@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>

EmulatorPkg/Library/PlatformBmLib/PlatformBm.c

@@ -332,6 +332,35 @@ PlatformBdsRegisterStaticBootOptions (
   PrintXY (10, 50, &White, &Black, L"Enter to boot directly.");
 }
 
+/**
+  Returns the priority number.
+
+  @param BootOption
+**/
+UINTN
+BootOptionPriority (
+  CONST EFI_BOOT_MANAGER_LOAD_OPTION *BootOption
+  )
+{
+  //
+  // Make sure Shell is first
+  //
+  if (StrCmp (BootOption->Description, L"UEFI Shell") == 0) {
+    return 0;
+  }
+  return 100;
+}
+
+INTN
+EFIAPI
+CompareBootOption (
+  CONST EFI_BOOT_MANAGER_LOAD_OPTION  *Left,
+  CONST EFI_BOOT_MANAGER_LOAD_OPTION  *Right
+  )
+{
+  return BootOptionPriority (Left) - BootOptionPriority (Right);
+}
+
 /**
   Do the platform specific action after the console is connected.
 
@@ -377,6 +406,7 @@ PlatformBootManagerAfterConsole (
     PlatformBdsRegisterStaticBootOptions ();
     PlatformBdsConnectSequence ();
     EfiBootManagerRefreshAllBootOption ();
+    EfiBootManagerSortLoadOptionVariable (LoadOptionTypeBoot, (SORT_COMPARE)CompareBootOption);
     break;
   }
 }