--- a/browser/Makefile.in
+++ b/browser/Makefile.in
@@ -51,23 +51,24 @@ PARALLEL_DIRS = \
   themes \
   $(NULL)
 
 DIRS = \
   devtools \
   app \
   $(NULL)
 
-ifeq ($(OS_ARCH),WINNT)
+ifdef MAKENSISU
 DIRS += installer/windows
 endif
 
 include $(topsrcdir)/config/rules.mk
 
-ifeq ($(OS_ARCH),WINNT)
+ifdef MAKENSISU
+
 # For Windows build the uninstaller during the application build since the
 # uninstaller is included with the application for mar file generation.
 libs::
 	$(MAKE) -C installer/windows uninstaller
 ifdef MOZ_MAINTENANCE_SERVICE
 	$(MAKE) -C installer/windows maintenanceservice_installer
 endif
 endif

--- a/browser/makefiles.sh
+++ b/browser/makefiles.sh
@@ -97,17 +97,17 @@ security/manager/locales/Makefile
 "
 
 if [ "$MOZ_SAFE_BROWSING" ]; then
   add_makefiles "
     browser/components/safebrowsing/Makefile
   "
 fi
 
-if [ "$MOZ_WIDGET_TOOLKIT" = "windows" ]; then
+if [ "$MAKENSISU" ]; then
   add_makefiles "
     browser/installer/windows/Makefile
   "
 fi
 
 if [ "$MOZ_WIDGET_TOOLKIT" = "gtk2" -o "$MOZ_WIDGET_TOOLKIT" = "qt" ]; then
   add_makefiles "
     browser/themes/gnomestripe/Makefile

--- a/configure.in
+++ b/configure.in
@@ -6314,39 +6314,48 @@ if test -n "$MOZ_TREE_FREETYPE"; then
    AC_DEFINE(HAVE_FT_LOAD_SFNT_TABLE)
    AC_SUBST(CAIRO_FT_CFLAGS)
 fi
 
 dnl ========================================================
 dnl Installer
 dnl ========================================================
 dnl Abort Windows build if the required major version and
-dnl minimum minor version of Unicode NSIS isn't in the path.
+dnl minimum minor version of Unicode NSIS isn't in the path
+dnl (unless in case of cross compiling, for which Unicode
+dnl is not yet sufficient).
 if test "$OS_ARCH" = "WINNT"; then
     REQ_NSIS_MAJOR_VER=2
     MIN_NSIS_MINOR_VER=33
     MOZ_PATH_PROGS(MAKENSISU, $MAKENSISU makensisu-2.46 makensisu makensis)
-    if test -z "$MAKENSISU" -o "$MAKENSISU" = ":"; then
-        AC_MSG_ERROR([To build the installer you must have the latest MozillaBuild or Unicode NSIS with a major version of $REQ_NSIS_MAJOR_VER and a minimum minor version of $MIN_NSIS_MINOR_VER in your path.])
-    fi
-    changequote(,)
-    MAKENSISU_VER=`"$MAKENSISU" -version 2>/dev/null | sed -e '/-Unicode/!s/.*//g' -e 's/^v\([0-9]\+\.[0-9]\+\)\-Unicode$/\1/g'`
-    changequote([,])
-    if test ! "$MAKENSISU_VER" = ""; then
-        MAKENSISU_MAJOR_VER=`echo $MAKENSISU_VER | $AWK -F\. '{ print $1 }'`
-        MAKENSISU_MINOR_VER=`echo $MAKENSISU_VER | $AWK -F\. '{ print $2 }'`
-    fi
-    AC_MSG_CHECKING([for Unicode NSIS with major version == $REQ_NSIS_MAJOR_VER and minor version >= $MIN_NSIS_MINOR_VER])
-    if test "$MAKENSISU_VER" = "" ||
-       test ! "$MAKENSISU_MAJOR_VER" = "$REQ_NSIS_MAJOR_VER" -o \
-            ! "$MAKENSISU_MINOR_VER" -ge $MIN_NSIS_MINOR_VER; then
-        AC_MSG_RESULT([no])
-        AC_MSG_ERROR([To build the installer you must have the latest MozillaBuild or Unicode NSIS with a major version of $REQ_NSIS_MAJOR_VER and a minimum minor version of $MIN_NSIS_MINOR_VER in your path.])
-    fi
-    AC_MSG_RESULT([yes])
+    if test -n "$MAKENSISU" -a "$MAKENSISU" != ":"; then
+      AC_MSG_RESULT([yes])
+      changequote(,)
+      MAKENSISU_VER=`"$MAKENSISU" -version 2>/dev/null | sed -e '/-Unicode/!s/.*//g' -e 's/^v\([0-9]\+\.[0-9]\+\)\-Unicode$/\1/g'`
+      changequote([,])
+      if test ! "$MAKENSISU_VER" = ""; then
+          MAKENSISU_MAJOR_VER=`echo $MAKENSISU_VER | $AWK -F\. '{ print $1 }'`
+          MAKENSISU_MINOR_VER=`echo $MAKENSISU_VER | $AWK -F\. '{ print $2 }'`
+      fi
+      AC_MSG_CHECKING([for Unicode NSIS with major version == $REQ_NSIS_MAJOR_VER and minor version >= $MIN_NSIS_MINOR_VER])
+      if test "$MAKENSISU_VER" = "" || \
+         test ! "$MAKENSISU_MAJOR_VER" = "$REQ_NSIS_MAJOR_VER" -o \
+              ! "$MAKENSISU_MINOR_VER" -ge $MIN_NSIS_MINOR_VER; then
+          AC_MSG_RESULT([no])
+          if test -z "$CROSS_COMPILE"; then
+            AC_MSG_ERROR([To build the installer you must have the latest MozillaBuild or Unicode NSIS with a major version of $REQ_NSIS_MAJOR_VER and a minimum minor version of $MIN_NSIS_MINOR_VER in your path.])
+          else
+            MAKENSISU=
+          fi
+      fi
+    elif test -z "$CROSS_COMPILE"; then
+      AC_MSG_ERROR([To build the installer you must have the latest MozillaBuild or Unicode NSIS with a major version of $REQ_NSIS_MAJOR_VER and a minimum minor version of $MIN_NSIS_MINOR_VER in your path.])
+    else
+      MAKENSISU=
+    fi
 fi
 
 AC_MSG_CHECKING([for tar archiver])
 AC_CHECK_PROGS(TAR, gnutar gtar tar, "")
 if test -z "$TAR"; then
     AC_MSG_ERROR([no tar archiver found in \$PATH])
 fi
 AC_MSG_RESULT([$TAR])

--- a/xulrunner/Makefile.in
+++ b/xulrunner/Makefile.in
@@ -45,17 +45,17 @@ include $(DEPTH)/config/autoconf.mk
 
 PARALLEL_DIRS = \
   app \
   setup \
   stub \
   examples \
   $(NULL)
 
-ifeq ($(OS_ARCH),WINNT)
+ifdef MAKENSISU
 DIRS += installer/windows
 endif
 
 ifeq ($(OS_ARCH),WINNT)
 PARALLEL_DIRS += tools/redit
 endif
 
 include $(topsrcdir)/config/rules.mk

--- a/xulrunner/makefiles.sh
+++ b/xulrunner/makefiles.sh
@@ -47,17 +47,17 @@ xulrunner/examples/simple/Makefile
 xulrunner/examples/simple/components/Makefile
 xulrunner/examples/simple/components/public/Makefile
 xulrunner/examples/simple/components/src/Makefile
 xulrunner/setup/Makefile
 xulrunner/stub/Makefile
 xulrunner/installer/Makefile
 "
 
-if [ "$OS_ARCH" = "WINNT" ]; then
+if [ "$MAKENSISU" ]; then
   add_makefiles "
     xulrunner/installer/windows/Makefile
   "
 fi
 
 if [ "$OS_ARCH" = "Darwin" ]; then
   add_makefiles "
     xulrunner/installer/mac/Makefile