finish enabling -C rpath by default in rustc. See rust-lang#30353.

pnkfelix · pnkfelix · commit b043ded80269 · 2016-01-06T16:24:18.000+01:00
diff --git a/mk/main.mk b/mk/main.mk
@@ -149,7 +149,7 @@ endif
 ifdef TRACE
   CFG_RUSTC_FLAGS += -Z trace
 endif
-ifdef CFG_ENABLE_RPATH
+ifndef CFG_DISABLE_RPATH
 CFG_RUSTC_FLAGS += -C rpath
 endif
 
