--- a/js/src/old-configure.in
+++ b/js/src/old-configure.in
@@ -1919,42 +1919,16 @@ MOZ_ARG_ENABLE_STRING([update-channel],
     MOZ_UPDATE_CHANNEL=`echo $enableval | tr A-Z a-z`)
 
 if test -z "$MOZ_UPDATE_CHANNEL"; then
     MOZ_UPDATE_CHANNEL=default
 fi
 AC_DEFINE_UNQUOTED(MOZ_UPDATE_CHANNEL, $MOZ_UPDATE_CHANNEL)
 AC_SUBST(MOZ_UPDATE_CHANNEL)
 
-
-dnl set GRE_MILESTONE
-dnl ========================================================
-GRE_MILESTONE=`tail -n 1 "$_topsrcdir"/config/milestone.txt 2>/dev/null || tail -1 "$_topsrcdir"/config/milestone.txt`
-AC_SUBST(GRE_MILESTONE)
-
-dnl set RELEASE_BUILD and NIGHTLY_BUILD variables depending on the cycle we're in
-dnl The logic works like this:
-dnl - if we have "a1" in GRE_MILESTONE, we're building Nightly (define NIGHTLY_BUILD)
-dnl - otherwise, if we have "a" in GRE_MILESTONE, we're building Nightly or Aurora
-dnl - otherwise, we're building Release/Beta (define RELEASE_BUILD)
-case "$GRE_MILESTONE" in
-  *a1*)
-      NIGHTLY_BUILD=1
-      AC_DEFINE(NIGHTLY_BUILD)
-      ;;
-  *a*)
-      ;;
-  *)
-      RELEASE_BUILD=1
-      AC_DEFINE(RELEASE_BUILD)
-      ;;
-esac
-AC_SUBST(NIGHTLY_BUILD)
-AC_SUBST(RELEASE_BUILD)
-
 dnl ========================================================
 dnl =
 dnl = Check for external package dependencies
 dnl =
 dnl ========================================================
 MOZ_ARG_HEADER(External Packages)
 
 MOZ_CONFIG_NSPR(js)

--- a/moz.configure
+++ b/moz.configure
@@ -10,16 +10,59 @@ include('build/moz.configure/checks.conf
 # Note:
 # - Gecko-specific options and rules should go in toolkit/moz.configure.
 # - Firefox-specific options and rules should go in browser/moz.configure.
 # - Fennec-specific options and rules should go in
 #   mobile/android/moz.configure.
 # - Spidermonkey-specific options and rules should go in js/moz.configure.
 # - etc.
 
+# set RELEASE_BUILD and NIGHTLY_BUILD variables depending on the cycle we're in
+# The logic works like this:
+# - if we have "a1" in GRE_MILESTONE, we're building Nightly (define NIGHTLY_BUILD)
+# - otherwise, if we have "a" in GRE_MILESTONE, we're building Nightly or Aurora
+# - otherwise, we're building Release/Beta (define RELEASE_BUILD)
+@depends(check_build_environment)
+@advanced
+def milestone(build_env):
+    add_old_configure_assignment('MOZ_CHROME_FILE_FORMAT', 'flat')
+    milestone_path = os.path.join(build_env['TOPSRCDIR'],
+                                  'config',
+                                  'milestone.txt')
+    with open(milestone_path, 'r') as fh:
+        milestone = fh.read().splitlines()[-1]
+
+    set_config('GRE_MILESTONE', milestone)
+
+    is_nightly, is_release = False, False
+
+    if 'a1' in milestone:
+        set_config('NIGHTLY_BUILD', '1')
+        set_define('NIGHTLY_BUILD', '1')
+        add_old_configure_assignment('NIGHTLY_BUILD', '1')
+        is_nightly = True
+    elif 'a' not in milestone:
+        set_config('RELEASE_BUILD', '1')
+        set_define('RELEASE_BUILD', '1')
+        add_old_configure_assignment('RELEASE_BUILD', '1')
+        is_release = True
+
+    return namespace(version=milestone,
+                     is_nightly=is_nightly,
+                     is_release=is_release)
+
+# Multiprocess Firefox Testing UI - Nightly and Aurora
+# To be removed in Bug 1003313
+@depends(milestone)
+def e10s_testing_only(milestone):
+    if not milestone.is_release:
+        set_config('E10S_TESTING_ONLY', '1')
+        set_define('E10S_TESTING_ONLY', '1')
+
+
 option('--enable-artifact-builds', env='MOZ_ARTIFACT_BUILDS',
        help='Download and use prebuilt binary artifacts.')
 
 @depends('--enable-artifact-builds')
 def artifact_builds(value):
     if value:
         imply_option('--disable-compile-environment')
         set_config('MOZ_ARTIFACT_BUILDS', '1')

--- a/old-configure.in
+++ b/old-configure.in
@@ -2695,52 +2695,16 @@ WINNT|Darwin|Android)
   ;;
 *)
   MOZ_FOLD_LIBS=
   ;;
 esac
 
 MOZ_CONFIG_NSPR()
 
-dnl set GRE_MILESTONE
-dnl ========================================================
-GRE_MILESTONE=`tail -n 1 "$_topsrcdir"/config/milestone.txt 2>/dev/null || tail -1 "$_topsrcdir"/config/milestone.txt`
-AC_SUBST(GRE_MILESTONE)
-
-# set RELEASE_BUILD and NIGHTLY_BUILD variables depending on the cycle we're in
-# The logic works like this:
-# - if we have "a1" in GRE_MILESTONE, we're building Nightly (define NIGHTLY_BUILD)
-# - otherwise, if we have "a" in GRE_MILESTONE, we're building Nightly or Aurora
-# - otherwise, we're building Release/Beta (define RELEASE_BUILD)
-case "$GRE_MILESTONE" in
-  *a1*)
-      NIGHTLY_BUILD=1
-      AC_DEFINE(NIGHTLY_BUILD)
-      ;;
-  *a*)
-      ;;
-  *)
-      RELEASE_BUILD=1
-      AC_DEFINE(RELEASE_BUILD)
-      ;;
-esac
-AC_SUBST(NIGHTLY_BUILD)
-AC_SUBST(RELEASE_BUILD)
-
-dnl ========================================================
-dnl Multiprocess Firefox Testing UI - Nightly and Aurora
-dnl To be removed in Bug 1003313
-dnl ========================================================
-if test -z "$RELEASE_BUILD"; then
-    E10S_TESTING_ONLY=1
-    AC_DEFINE(E10S_TESTING_ONLY)
-fi
-
-AC_SUBST(E10S_TESTING_ONLY)
-
 dnl ========================================================
 dnl system libevent Support
 dnl ========================================================
 MOZ_ARG_WITH_STRING(system-libevent,
 [  --with-system-libevent[=PFX]
                           Use system libevent [installed at prefix PFX]],
     LIBEVENT_DIR=$withval)