X.org: needs dynamic library support

xlib_libX11, one of the main libraries of X.org, uses dlfcn.h and dlopen.
To avoid having to add a dependency on !BR2_PREFER_STATIC_LIB on tons of
packages, we promote this dependency to X.org itself (similar to how thread
support is handled in X.org).

Fixes
http://autobuild.buildroot.net/results/a47/a47c5d96f880af04b85bb6773e87d04f9d7c2864/

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/x11r7/Config.in

@@ -2,6 +2,7 @@ menuconfig BR2_PACKAGE_XORG7
 	bool "X.org X Window System"
 	depends on BR2_USE_WCHAR
 	depends on BR2_TOOLCHAIN_HAS_THREADS
+	depends on !BR2_PREFER_STATIC_LIB # dlopen in xlib_libX11
 	help
 	  Support for X11R7 libraries, servers, drivers, and/or
 	  applications in the target.
@@ -262,5 +263,5 @@ if BR2_PACKAGE_XORG7
 	endmenu
 endif
 
-comment "X.org needs a toolchain w/ wchar, threads"
-	depends on !BR2_USE_WCHAR || !BR2_TOOLCHAIN_HAS_THREADS
+comment "X.org needs a toolchain w/ wchar, threads, dynamic library"
+	depends on !BR2_USE_WCHAR || !BR2_TOOLCHAIN_HAS_THREADS || BR2_PREFER_STATIC_LIB