Pass --as-needed by default to the linker.

--- gcc/config/mips/linux.h
+++ gcc/config/mips/linux.h
@@ -67,6 +67,7 @@
 #undef LINK_SPEC
 #define LINK_SPEC \
  "%(endian_spec) \
+  --as-needed \
   %{shared:-shared} \
   %{!shared: \
     %{!static: \