[cmake] Use source-groups in Polly.

Configure CMake to setup source-groups for Polly. Source groups
describe how source files should be organized in IDEs. By default, all
headers are dumped into one folder under PollyCore and all source files
into another. On disk, these files are organized into folders, but this
isn't reflected in the IDE. This change uses CMake source groups to have
the IDE reflect the on disk layout. This will make it easier to visualize
the project structure for users of Visual Studio and XCode

Patch by Christopher Tetreault <ctetreau@quicinc.com>

Reviewed By: Meinersbur, grosser

Differential Revision: https://reviews.llvm.org/D72117

GitOrigin-RevId: 76ee0de00c407399b0aa7d282c589739b818b3dc
2 files changed