[build] Move pm depfile to outdir

Move the depfile written by pm to the target_out_dir.

Change-Id: Ie9f89e590f0b9461862ce55bedd41473aa3cd1dd
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/694044
Fuchsia-Auto-Submit: Aaron Wood <aaronwood@google.com>
Commit-Queue: Auto-Submit <auto-submit@fuchsia-infra.iam.gserviceaccount.com>
Reviewed-by: Jay Zhuang <jayzhuang@google.com>
diff --git a/src/sys/pkg/bin/pm/pm.gni b/src/sys/pkg/bin/pm/pm.gni
index df6ba41..af9f609c 100644
--- a/src/sys/pkg/bin/pm/pm.gni
+++ b/src/sys/pkg/bin/pm/pm.gni
@@ -313,7 +313,7 @@
                              "testonly",
                              "visibility",
                            ])
-    depfile = "${target_gen_dir}/${target_name}.d"
+    depfile = "${target_out_dir}/${target_name}.d"
 
     assert(inputs == [ inputs[0] ],
            "pm_publish(\"$target_name\") requires exactly one input")