Our automake-1.11.2 doesn't support it yet, see:
http://lists.gnu.org/archive/html/automake/2011-12/msg00081.html

Upstream-Status: Inappropriate [fix or upgrade oe-core automake]

diff -uNr ImageMagick-6.7.5-6.orig/configure.ac ImageMagick-6.7.5-6/configure.ac
--- ImageMagick-6.7.5-6.orig/configure.ac	2012-02-12 18:07:28.000000000 +0100
+++ ImageMagick-6.7.5-6/configure.ac	2012-02-15 12:55:47.668813474 +0100
@@ -128,7 +128,7 @@
 # Ensure that make can run correctly
 AM_SANITY_CHECK
 
-AM_INIT_AUTOMAKE([1.11 color-tests foreign parallel-tests silent-rules subdir-objects dist-bzip2 dist-lzip dist-xz dist-zip])
+AM_INIT_AUTOMAKE([1.11 color-tests foreign parallel-tests silent-rules subdir-objects dist-bzip2 dist-xz dist-zip])
 
 # Enable support for silent build rules
 m4_ifdef([AM_SILENT_RULES],[AM_SILENT_RULES([yes])])
