Copy files instead of hard-linking on Windows

Fixes an issue on Windows where when source and build directory are on different drives hard-linking
to files or directory fails as it doesn't work across filesystem boundaries. Note that symlinking is also
not possible because it requires administrator privileges on Windows.

The solution copies the files using the built-in cmake `configure_file(src dest COPYONLY)` command.
As this command only operates on files, if a directory is specified the files will be globbed recursively
and through symlinks.

Signed-off-by: Dominik Gschwind <dominik.gschwind99@gmail.com>
diff --git a/ChangeLog.d/fix_hard_link_across_drives b/ChangeLog.d/fix_hard_link_across_drives
new file mode 100644
index 0000000..0c55c30
--- /dev/null
+++ b/ChangeLog.d/fix_hard_link_across_drives
@@ -0,0 +1,3 @@
+Bugfix
+   * Fix a build issue on Windows where the source and build directory could not be on
+     different drives (#5751).