BaseTools: Add the FeatureFlagExpression usage to the Source Section

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=3828

FeatureFlagExpression Support in Source section of INF file. The Pcd
value in the expression is from INF or DEC.
When a FeatureFlagExpression is present,if the expression evaluates
to TRUE,then the entry is valid. If the expression evaluates to FALSE,
then the EDK II build tools must ignore the entry.

This patch is going to add this feature.

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Heng Luo <heng.luo@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>
Signed-off-by: Yi Li <yi1.li@intel.com>

BaseTools/Source/Python/Workspace/MetaFileParser.py

@@ -736,6 +736,10 @@ class InfParser(MetaFileParser):
     @ParseMacro
     def _SourceFileParser(self):
         TokenList = GetSplitValueList(self._CurrentLine, TAB_VALUE_SPLIT)
+        # Let TokenList[2] be TagName|ToolCode|FeatureFlag
+        if len(TokenList) > 3:
+            for extraToken in range(3, len(TokenList)):
+                TokenList[2] = TokenList[2] + '|' + TokenList[extraToken]
         self._ValueList[0:len(TokenList)] = TokenList
         Macros = self._Macros
         # For Acpi tables, remove macro like ' TABLE_NAME=Sata1'