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

--- gcc/config/mips/gnu-user.h
+++ gcc/config/mips/gnu-user.h
@@ -54,7 +54,7 @@
 
 #undef GNU_USER_TARGET_LINK_SPEC
 #define GNU_USER_TARGET_LINK_SPEC "\
-  %{G*} %{EB} %{EL} %{mips*} %{shared} \
+  %{G*} %{EB} %{EL} %{mips*} --as-needed %{shared} \
   %{!shared: \
     %{!static: \
       %{rdynamic:-export-dynamic} \