BaseTools: Syntax warning invalid escape sequence \C

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4666

This commit fixes the issue reported through BZ4666.
The Syntax warning related to invalid escape sequence
for \C is seen on Windows OS based builds of edk2 sources.
On Windows the path seperator needs to prefixed with \
so essentially we need to use \\ as path seperator.

Cc: Rebecca Cran <[email protected]>
Cc: Michael D Kinney <[email protected]>
Cc: Laszlo Ersek <[email protected]>
Cc: Liming Gao <[email protected]>
Cc: Bob Feng <[email protected]>
Cc: Yuwei Chen <[email protected]>
Cc: Jayaprakash N <[email protected]>
Signed-off-by: Jayaprakash N <[email protected]>
Reviewed-by: Laszlo Ersek <[email protected]>
Reviewed-by: Rebecca Cran <[email protected]>

BaseTools/Source/Python/Workspace/DscBuildData.py

@@ -3033,7 +3033,7 @@ def GenerateByteArrayValue (self, StructuredPcds):
             StructuredPcdsData["OBJECTS"][include_file] = os.path.getmtime(include_file)
             MakeApp += "$(OBJECTS) : %s\n" % include_file
         if sys.platform == "win32":
-            PcdValueCommonPath = os.path.normpath(mws.join(GlobalData.gGlobalDefines["EDK_TOOLS_PATH"], "Source\C\Common\PcdValueCommon.c"))
+            PcdValueCommonPath = os.path.normpath(mws.join(GlobalData.gGlobalDefines["EDK_TOOLS_PATH"], "Source\\C\\Common\\PcdValueCommon.c"))
             MakeApp = MakeApp + '%s\\PcdValueCommon.c : %s\n' % (self.OutputPath, PcdValueCommonPath)
             MakeApp = MakeApp + '\tcopy /y %s $@\n' % (PcdValueCommonPath)
         else: