package/freerdp: can not build on uClibc

FreeRDP uses eventfd_{read,write}, which is not supported in uClibc.

Fixes:
    http://autobuild.buildroot.net/results/ad7/ad7ade4c436d21cba930f40c613870fbadec840e/
    http://autobuild.buildroot.net/results/5a3/5a30aecbb426f76a22e8285931a0a8cd59b5e70b/
    http://autobuild.buildroot.net/results/6e0/6e0de0538e95ae156f7d2ad6eede46e44be81c8e/
    [...]

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/freerdp/Config.in

@@ -7,8 +7,13 @@ config BR2_PACKAGE_FREERDP
 	select BR2_PACKAGE_XLIB_LIBXCURSOR
 	select BR2_PACKAGE_ZLIB
 	depends on BR2_PACKAGE_XORG7
+	depends on !BR2_TOOLCHAIN_USES_UCLIBC # evenft_{read,write}
 	help
 	  FreeRDP is a free implementation of the Remote Desktop
 	  Protocol (RDP), released under the Apache license
 
 	  http://www.freerdp.com/
+
+comment "freerdp needs an (e)glibc or musl toolchain"
+	depends on BR2_PACKAGE_XORG7
+	depends on BR2_TOOLCHAIN_USES_UCLIBC