deleted file mode 100755
--- a/build/unix/uniq.py
+++ /dev/null
@@ -1,10 +0,0 @@
-#! /usr/bin/env python
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-'''Prints the given arguments in sorted order with duplicates removed.'''
-
-import sys
-
-print(' '.join(sorted(set(sys.argv[1:]))))

--- a/configure.in
+++ b/configure.in
@@ -6301,19 +6301,16 @@ if test -n "$LIBXUL_SDK_DIR" -a `echo "$
 fi
 
 if test `echo "$MOZ_EXTENSIONS" | grep -c gio` -ne 0; then
     MOZ_GIO_COMPONENT=1
     MOZ_EXTENSIONS=`echo $MOZ_EXTENSIONS | sed -e 's|gio||'`
 fi
 AC_SUBST(MOZ_GIO_COMPONENT)
 
-dnl Remove dupes
-MOZ_EXTENSIONS=`$PYTHON ${srcdir}/build/unix/uniq.py ${MOZ_EXTENSIONS}`
-
 dnl Ensure every extension exists, to avoid mostly-inscrutable error messages
 dnl when trying to build a nonexistent extension.
 for extension in $MOZ_EXTENSIONS; do
     if test ! -d "${srcdir}/extensions/${extension}"; then
         AC_MSG_ERROR([Unrecognized extension provided to --enable-extensions: ${extension}.])
     fi
 done
 
@@ -8374,18 +8371,16 @@ MOZ_ARG_ENABLE_STRING(necko-protocols,
     elif test `echo "$option" | grep -c \^-` != 0; then
         option=`echo $option | sed 's/^-//'`
         NECKO_PROTOCOLS=`echo "$NECKO_PROTOCOLS" | sed "s/ ${option}//"`
     else
         NECKO_PROTOCOLS="$NECKO_PROTOCOLS $option"
     fi
 done],
     NECKO_PROTOCOLS="$NECKO_PROTOCOLS_DEFAULT")
-dnl Remove dupes
-NECKO_PROTOCOLS=`$PYTHON ${srcdir}/build/unix/uniq.py ${NECKO_PROTOCOLS}`
 AC_SUBST_SET(NECKO_PROTOCOLS)
 for p in $NECKO_PROTOCOLS; do
     AC_DEFINE_UNQUOTED(NECKO_PROTOCOL_$p)
     _NON_GLOBAL_ACDEFINES="$_NON_GLOBAL_ACDEFINES NECKO_PROTOCOL_$p"
 done
 
 dnl
 dnl option to disable necko's wifi scanner
@@ -8559,17 +8554,17 @@ AC_SUBST(MOZ_UPDATE_XTERM)
 AC_SUBST(MOZ_AUTH_EXTENSION)
 AC_SUBST(MOZ_PREF_EXTENSIONS)
 AC_SUBST(MOZ_DEBUG)
 AC_SUBST(MOZ_DEBUG_SYMBOLS)
 AC_SUBST(MOZ_DEBUG_ENABLE_DEFS)
 AC_SUBST(MOZ_DEBUG_DISABLE_DEFS)
 AC_SUBST(MOZ_DEBUG_LDFLAGS)
 AC_SUBST(WARNINGS_AS_ERRORS)
-AC_SUBST(MOZ_EXTENSIONS)
+AC_SUBST_SET(MOZ_EXTENSIONS)
 AC_SUBST(MOZ_ENABLE_PROFILER_SPS)
 AC_SUBST(MOZ_JPROF)
 AC_SUBST(MOZ_INSTRUMENTS)
 AC_SUBST(MOZ_CALLGRIND)
 AC_SUBST(MOZ_VTUNE)
 AC_SUBST(MOZ_PROFILING)
 AC_SUBST(LIBICONV)
 AC_SUBST(MOZ_PLACES)

--- a/extensions/moz.build
+++ b/extensions/moz.build
@@ -1,7 +1,7 @@
 # -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
 # vim: set filetype=python:
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-DIRS += CONFIG['MOZ_EXTENSIONS'].split()
+DIRS += CONFIG['MOZ_EXTENSIONS']