ExternalData: Clean up duplicate regex matches with CMAKE_MATCH_<n>
ExternalData: Clean up duplicate regex matches with CMAKE_MATCH_<n>

The matches have already been calculated and can simply be taken from
CMAKE_MATCH_n variables. This avoids multiple compilations of the same or very
similar regular expressions.

Change-Id: Ie9d66cc5790475307eaea1c8c934ed16b28ae5f2

msmolens/VTK,gram526/VTK,SimVascular/VTK,SimVascular/VTK,mspark93/VTK,jmerkow/VTK,gram526/VTK,mspark93/VTK,jmerkow/VTK,candy7393/VTK,sankhesh/VTK,mspark93/VTK,sumedhasingla/VTK,demarle/VTK,jmerkow/VTK,msmolens/VTK,keithroe/vtkoptix,gram526/VTK,SimVascular/VTK,gram526/VTK,sumedhasingla/VTK,mspark93/VTK,jmerkow/VTK,demarle/VTK,msmolens/VTK,mspark93/VTK,candy7393/VTK,candy7393/VTK,keithroe/vtkoptix,sumedhasingla/VTK,keithroe/vtkoptix,mspark93/VTK,sumedhasingla/VTK,demarle/VTK,sumedhasingla/VTK,candy7393/VTK,SimVascular/VTK,keithroe/vtkoptix,gram526/VTK,msmolens/VTK,candy7393/VTK,demarle/VTK,sankhesh/VTK,candy7393/VTK,candy7393/VTK,SimVascular/VTK,keithroe/vtkoptix,jmerkow/VTK,gram526/VTK,sankhesh/VTK,msmolens/VTK,gram526/VTK,SimVascular/VTK,SimVascular/VTK,demarle/VTK,SimVascular/VTK,msmolens/VTK,sankhesh/VTK,candy7393/VTK,mspark93/VTK,sankhesh/VTK,sankhesh/VTK,keithroe/vtkoptix,demarle/VTK,sankhesh/VTK,mspark93/VTK,msmolens/VTK,jmerkow/VTK,gram526/VTK,sumedhasingla/VTK,jmerkow/VTK,sumedhasingla/VTK,jmerkow/VTK,sumedhasingla/VTK,keithroe/vtkoptix,keithroe/vtkoptix,msmolens/VTK,demarle/VTK,sankhesh/VTK,demarle/VTK