BaseTools/Upt: Add a BOM check for UNI file and fix some help message error

Add a BOM check for UNI file and fix some help message error

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hess Chen <hesheng.chen@intel.com>
Reviewed-by: YangX Li <yangx.li@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17876 6f19259b-4bc3-4df7-8a09-765794883524

BaseTools/Source/Python/UPT/Library/ParserValidate.py

@@ -721,3 +721,12 @@ def IsValidUserId(UserId):
             return False
     return True
 
+#
+# Check if a UTF16-LE file has a BOM header
+#
+def CheckUTF16FileHeader(File):
+    FileIn = open(File, 'rb').read(2)
+    if FileIn != '\xff\xfe':
+        return False
+
+    return True