package/uvw: needs C++

Fixes:
 - http://autobuild.buildroot.org/results/01f97d793f28772cfce44f6979e39d8adff233af

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/uvw/Config.in

@@ -3,6 +3,7 @@ config BR2_PACKAGE_UVW
 	depends on BR2_TOOLCHAIN_HAS_THREADS_NPTL # libuv
 	depends on BR2_USE_MMU # libuv
 	depends on !BR2_STATIC_LIBS # libuv
+	depends on BR2_INSTALL_LIBSTDCPP
 	depends on BR2_TOOLCHAIN_HAS_SYNC_4 # libuv
 	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_7 # C++17
 	select BR2_PACKAGE_LIBUV
@@ -12,8 +13,8 @@ config BR2_PACKAGE_UVW
 
 	  https://github.com/skypjack/uvw
 
-comment "uvw needs a toolchain w/ NPTL, dynamic library, gcc >= 7"
+comment "uvw needs a toolchain w/ NPTL, dynamic library, C++, gcc >= 7"
 	depends on !BR2_TOOLCHAIN_HAS_THREADS_NPTL || BR2_STATIC_LIBS || \
-		!BR2_TOOLCHAIN_GCC_AT_LEAST_7
+		!BR2_INSTALL_LIBSTDCPP || !BR2_TOOLCHAIN_GCC_AT_LEAST_7
 	depends on BR2_USE_MMU
 	depends on BR2_TOOLCHAIN_HAS_SYNC_4