Build information: compiler and CUDA version in rugnux's log and banner, the broker's and writer's start, the viewer's About

GitInfo gains jfjoch_build_compiler() (CMake's compiler id and version), jfjoch_build_cuda() (the CUDA
toolkit version, empty without CUDA) and jfjoch_build_info(with_cuda), one line of compiler, CUDA and flags,
stamped like the git hash. rugnux logs it as "Build:" (beside the "Build flags:" line the timing table
reads) and prints it under its version; jfjoch_broker and jfjoch_writer (without CUDA, which it does not
use) log it at start; jfjoch_viewer shows it in About. Nothing is written into the output files.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PXc1zD1yxHqaR1DGdCTHL4

viewer/JFJochViewerMenu.cpp

@@ -201,6 +201,7 @@ void JFJochViewerMenu::aboutSelected() {
 
     QString about_text = "<h3>Jungfraujoch Image Viewer</h3>" // Use HTML for improved style
         "<p><b>Version:</b> " + version + "</p>"
+        "<p><b>Build:</b> " + QString::fromStdString(jfjoch_build_info(true)).toHtmlEscaped() + "</p>"
         "<p><b>Copyright:</b> 2019-2025 Paul Scherrer Institute</p>"
         "<p><b>Author:</b> Filip Leonarski &lt;filip.leonarski@psi.ch&gt;</p>"
         "<p><b>Links:</b> <a href='https://jungfraujoch.readthedocs.io'>Documentation</a>, "