BaseTools: Align include guards policy

The EDK II C Coding Standards Specification states that:
"Names starting with one or two underscores, such as
_MACRO_GUARD_FILE_NAME_H_, must not be used. They are
reserved for compiler implementation." [1]

The Ecc tool currently checks that the include guard end with
a trailing underscore. Thus, the check and the error message
should both be modified.

The new check forces having one sole trailing underscore
character, as the example in the specification shows:
"FILE_NAME_H_" [1]
This would allow to have more consistency.

[1] Section 5.3.5 "All include file contents must be protected
by a #include guard":
https://edk2-docs.gitbook.io/
edk-ii-c-coding-standards-specification/5_source_files/53_include_files

Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
Reviewed-by: Sami Mujawar <Sami.Mujawar@arm.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>

BaseTools/Source/Python/Ecc/Check.py

@@ -1,6 +1,7 @@
 ## @file
 # This file is used to define checkpoints used by ECC tool
 #
+# Copyright (c) 2021, Arm Limited. All rights reserved.<BR>
 # Copyright (c) 2008 - 2020, Intel Corporation. All rights reserved.<BR>
 # SPDX-License-Identifier: BSD-2-Clause-Patent
 #
@@ -1438,7 +1439,7 @@ class Check(object):
             RecordSet = EccGlobalData.gDb.TblFile.Exec(SqlCommand)
             for Record in RecordSet:
                 Name = Record[1].replace('#ifndef', '').strip()
-                if Name[-1] != '_':
+                if Name[0] == '_' or Name[-1] != '_' or Name[-2] == '_':
                     if not EccGlobalData.gException.IsException(ERROR_NAMING_CONVENTION_CHECK_IFNDEF_STATEMENT, Name):
                         EccGlobalData.gDb.TblReport.Insert(ERROR_NAMING_CONVENTION_CHECK_IFNDEF_STATEMENT, OtherMsg="The #ifndef name [%s] does not follow the rules" % (Name), BelongsToTable=FileTable, BelongsToItem=Record[0])