Specify export visibility flags only for shared builds.
Specify export visibility flags only for shared builds.

When building static builds, since the export visibilty flags are not set for
all libraries, we were getting warnings with mismatched visibility when linking
vtkpython statically. Overcome the issue by not sepecifying visbility flags for
static builds.

Change-Id: Ic993920fa51119d5002f28ee5996abeab1b3bb4e

jmerkow/VTK,ashray/VTK-EVM,biddisco/VTK,aashish24/VTK-old,ashray/VTK-EVM,msmolens/VTK,sankhesh/VTK,ashray/VTK-EVM,hendradarwin/VTK,candy7393/VTK,SimVascular/VTK,biddisco/VTK,aashish24/VTK-old,msmolens/VTK,hendradarwin/VTK,msmolens/VTK,SimVascular/VTK,berendkleinhaneveld/VTK,sumedhasingla/VTK,hendradarwin/VTK,sumedhasingla/VTK,sumedhasingla/VTK,keithroe/vtkoptix,gram526/VTK,jmerkow/VTK,msmolens/VTK,mspark93/VTK,demarle/VTK,ashray/VTK-EVM,keithroe/vtkoptix,jmerkow/VTK,collects/VTK,SimVascular/VTK,berendkleinhaneveld/VTK,mspark93/VTK,johnkit/vtk-dev,jmerkow/VTK,johnkit/vtk-dev,sumedhasingla/VTK,demarle/VTK,sumedhasingla/VTK,candy7393/VTK,johnkit/vtk-dev,candy7393/VTK,jmerkow/VTK,berendkleinhaneveld/VTK,keithroe/vtkoptix,mspark93/VTK,mspark93/VTK,biddisco/VTK,collects/VTK,sankhesh/VTK,keithroe/vtkoptix,johnkit/vtk-dev,sumedhasingla/VTK,candy7393/VTK,SimVascular/VTK,demarle/VTK,demarle/VTK,collects/VTK,sankhesh/VTK,demarle/VTK,keithroe/vtkoptix,demarle/VTK,msmolens/VTK,collects/VTK,gram526/VTK,jmerkow/VTK,msmolens/VTK,berendkleinhaneveld/VTK,gram526/VTK,gram526/VTK,hendradarwin/VTK,hendradarwin/VTK,candy7393/VTK,candy7393/VTK,SimVascular/VTK,johnkit/vtk-dev,candy7393/VTK,gram526/VTK,aashish24/VTK-old,hendradarwin/VTK,demarle/VTK,mspark93/VTK,johnkit/vtk-dev,sumedhasingla/VTK,aashish24/VTK-old,sankhesh/VTK,sumedhasingla/VTK,SimVascular/VTK,hendradarwin/VTK,sankhesh/VTK,keithroe/vtkoptix,jmerkow/VTK,mspark93/VTK,SimVascular/VTK,ashray/VTK-EVM,berendkleinhaneveld/VTK,biddisco/VTK,ashray/VTK-EVM,sankhesh/VTK,aashish24/VTK-old,candy7393/VTK,collects/VTK,gram526/VTK,mspark93/VTK,mspark93/VTK,msmolens/VTK,aashish24/VTK-old,keithroe/vtkoptix,biddisco/VTK,collects/VTK,ashray/VTK-EVM,johnkit/vtk-dev,gram526/VTK,berendkleinhaneveld/VTK,biddisco/VTK,jmerkow/VTK,msmolens/VTK,gram526/VTK,keithroe/vtkoptix,sankhesh/VTK,SimVascular/VTK,berendkleinhaneveld/VTK,biddisco/VTK,sankhesh/VTK,ashray/VTK-EVM,demarle/VTK