BaseTools: Update Build tool to support multiple workspaces

WORKSPACE is still kept.
New PACKAGES_PATH is introduced to specify the additional WORKSPACEs.
In PACKAGES_PATH, ';' is separator in Windows, ':' is separator in Linux.

Build directory is in WORKSPACE. Package, BaseTools and Conf directory
will be found from WORKSPACE and PACKAGES_PATH.

In implementation, BaseTools adds MultipleWorkspace class for
the file path conversion from WORKSPACE and PACKAGES_PATH.

Verify two tree layouts.
Root\edk2\MdePkg
Root\edk2\MdeMdeModulePkg
Root\edk2\...
1. set WORKSPACE=Root\edk2
2. set WORKSPACE=Root, and set PACKAGES_PATH=Root\edk2

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Li YangX <yangx.li@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18579 6f19259b-4bc3-4df7-8a09-765794883524

BaseTools/Source/Python/GenFds/Region.py

@@ -24,6 +24,7 @@ from stat import *
 from Common import EdkLogger
 from Common.BuildToolError import *
 from Common.LongFilePathSupport import OpenLongFilePath as open
+from Common.MultipleWorkspace import MultipleWorkspace as mws
 
 ## generate Region
 #
@@ -205,7 +206,7 @@ class Region(RegionClassObject):
             for RegionData in self.RegionDataList:
                 RegionData = GenFdsGlobalVariable.MacroExtend(RegionData, MacroDict)
                 if RegionData[1] != ':' :
-                    RegionData = os.path.join (GenFdsGlobalVariable.WorkSpaceDir, RegionData)
+                    RegionData = mws.join (GenFdsGlobalVariable.WorkSpaceDir, RegionData)
                 if not os.path.exists(RegionData):
                     EdkLogger.error("GenFds", FILE_NOT_FOUND, ExtraData=RegionData)
                 #