linker: Use --as-needed by default when linker supports it

compiler/rustc_target/src/spec/redox_base.rs

@@ -5,14 +5,6 @@ pub fn opts() -> TargetOptions {
     args.insert(
         LinkerFlavor::Gcc,
         vec![
-            // We want to be able to strip as much executable code as possible
-            // from the linker command line, and this flag indicates to the
-            // linker that it can avoid linking in dynamic libraries that don't
-            // actually satisfy any symbols up to that point (as with many other
-            // resolutions the linker does). This option only applies to all
-            // following libraries so we're sure to pass it as one of the first
-            // arguments.
-            "-Wl,--as-needed".to_string(),
             // Always enable NX protection when it is available
             "-Wl,-z,noexecstack".to_string(),
         ],