Fixed an issue which will cause incorrect EFI_SOURCE, EDK_SOURCE and ECP_SOURCE value if the WORKSPACE is in the root of a drive, like "X:\"
Fixed an issue which will cause incorrect EFI_SOURCE, EDK_SOURCE and ECP_SOURCE value if the WORKSPACE is in the root of a drive, like "X:\"

git-svn-id: f3880c1fc5096ce2109c8aec392d8e07f619f417@1332 c2973edb-eda0-4c78-bc6a-9341b269661f

bitcrystal/buildtools-BaseTools,tianocore/buildtools-BaseTools,tianocore/buildtools-BaseTools,bitcrystal/buildtools-BaseTools,tianocore/buildtools-BaseTools,tianocore/buildtools-BaseTools,bitcrystal/buildtools-BaseTools,tianocore/buildtools-BaseTools,bitcrystal/buildtools-BaseTools,bitcrystal/buildtools-BaseTools