package/ncmpc: requires gcc >= 6

Following reply from upstream on build failure with gcc 5
(https://github.com/MusicPlayerDaemon/ncmpc/pull/47), enforce gcc >= 6

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/ncmpc/Config.in

@@ -4,7 +4,7 @@ config BR2_PACKAGE_NCMPC
 	depends on BR2_INSTALL_LIBSTDCPP
 	depends on BR2_USE_WCHAR # boost
 	depends on BR2_TOOLCHAIN_HAS_THREADS # boost
-	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_9 # C++14
+	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_6 # C++14
 	select BR2_PACKAGE_BOOST
 	select BR2_PACKAGE_BOOST_SYSTEM
 	select BR2_PACKAGE_LIBMPDCLIENT
@@ -16,7 +16,7 @@ config BR2_PACKAGE_NCMPC
 
 	  http://www.musicpd.org/clients/ncmpc/
 
-comment "ncmpc needs a toolchain w/ C++, wchar, threads, gcc >= 4.9"
+comment "ncmpc needs a toolchain w/ C++, wchar, threads, gcc >= 6"
 	depends on BR2_USE_MMU
 	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_USE_WCHAR || \
-		!BR2_TOOLCHAIN_HAS_THREADS || !BR2_TOOLCHAIN_GCC_AT_LEAST_4_9
+		!BR2_TOOLCHAIN_HAS_THREADS || !BR2_TOOLCHAIN_GCC_AT_LEAST_6