A64: Add back removed --gc-sections, which no longer upsets the Android gcc linker

build/android.gypi

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 238 matching lines @@
             ],
           }],
         ],
       }],  # _toolset=="target"
       # Settings for building host targets using the system toolchain.
       ['_toolset=="host"', {
         'cflags': [ '-m32', '-pthread' ],
         'ldflags': [ '-m32', '-pthread' ],
         'ldflags!': [
           '-Wl,-z,noexecstack',
+          '-Wl,--gc-sections',
           '-Wl,-O1',
           '-Wl,--as-needed',
         ],
       }],
     ],  # target_conditions
   },  # target_defaults
 }