package/librsync: not available in static builds

Upstream only supports shared builds:
https://github.com/librsync/librsync/blob/master/CMakeLists.txt#L319

Fixes
http://autobuild.buildroot.net/results/4b8/4b8db2d520373d0c9127e0d7695b5aeda6925dc5/

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
(cherry picked from commit f4573ea5d8f566d9d6de8013fc72f3d844702724)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/librsync/Config.in

@@ -1,5 +1,6 @@
 config BR2_PACKAGE_LIBRSYNC
 	bool "librsync"
+	depends on !BR2_STATIC_LIBS
 	select BR2_PACKAGE_ZLIB
 	select BR2_PACKAGE_BZIP2
 	select BR2_PACKAGE_POPT
@@ -9,3 +10,6 @@ config BR2_PACKAGE_LIBRSYNC
 	  rsync utility and is used in rproxy.
 
 	  https://github.com/librsync/librsync
+
+comment "librsync needs a toolchain w/ dynamic library support"
+	depends on BR2_STATIC_LIBS