[test] Fix dr324.c again for non-writeable source directories

[test] Fix dr324.c again for non-writeable source directories

In general, the source tree is not assumed to be writeable, so modifying `%s` does not work for all CI systems. Instead of touching `%s`, copy it to a writeable dir using `%t`, and touch it there.
Actually, `dr0xx.c` isn't really needed at all, so just create a new `dep.c` file in the build tree.

This was recently added in cb088e8c3abf30456e2891f90b5194d0070c387a, fixed in 1481fcf780bde7b115aa395064d71749b1a40889, and fixed again in d16c59013056f1bf8844ded8faeb0cf01b1c3613.