Quote the compile flags for Qt 5
Quote the compile flags for Qt 5

Otherwise, when the variable is empty it is an error.

Change-Id: I0523dcbdebaf86f1f5f089160b256562d9123002

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