Bug 1208566 - emit proper dependencies when compiling Rust sources; r=mshal

config/rules.mk

@@ -945,7 +945,7 @@ ifdef MOZ_RUST
 # in the target's LIBS.
 $(RSOBJS):
 	$(REPORT_BUILD)
-	$(RUSTC) $(RUSTFLAGS) --crate-type staticlib -o $(call mk_libname,$<) $(_VPATH_SRCS)
+	$(RUSTC) $(RUSTFLAGS) --crate-type staticlib --emit dep-info=$(MDDEPDIR)/$(call mk_libname,$<).pp,link=$(call mk_libname,$<) $(_VPATH_SRCS)
 endif
 
 $(SOBJS):