[ELF] --reproduce: strip directories for --dependency-file=

CMake may generate build.ninja with DEP_FILE specifying a non-existent
directory in the reproduce tarball.
diff --git a/lld/ELF/DriverUtils.cpp b/lld/ELF/DriverUtils.cpp
index 0278c07..4c88723 100644
--- a/lld/ELF/DriverUtils.cpp
+++ b/lld/ELF/DriverUtils.cpp
@@ -174,6 +174,7 @@
       break;
     case OPT_o:
     case OPT_Map:
+    case OPT_dependency_file:
     case OPT_print_archive_stats:
     case OPT_why_extract:
       // If an output path contains directories, "lld @response.txt" will