ci: Forward our dedicated license file to CPack packaging steps

This was missed in commit a9190bd38d (CMake: Prepare dedicated license
file for our own CPack configuration, 2025-03-02).

.gitlab/ci/package_windows_build.cmake

diff --git a/.gitlab/ci/package_windows_build.cmake b/.gitlab/ci/package_windows_build.cmake
index b881e21..a2b7ed4 100644
--- a/.gitlab/ci/package_windows_build.cmake
+++ b/.gitlab/ci/package_windows_build.cmake
@@ -4,8 +4,9 @@
 set(build "${CMAKE_CURRENT_BINARY_DIR}/build")
 
 file(GLOB paths RELATIVE "${CMAKE_CURRENT_BINARY_DIR}"
-  # Allow CPack to find CMAKE_ROOT.
+  # Allow CPack to find CMAKE_ROOT and license text.
   "${build}/CMakeFiles/CMakeSourceDir.txt"
+  "${build}/CMakeFiles/LICENSE.txt"
 
   # We need the main binaries.
   "${build}/bin"