package/rockchip-mali: needs C++

rockchip-mali pre-built libraries needs C++ since the addition of the
package in commit 97c74a73e5dee17530647f89b2c7d8692781eb14:

readelf -a output/build/rockchip-mali-721653b5b3b525a4f80d15aa7e2f9df7b7e60427/lib/aarch64-linux-gnu/libmali-bifrost-g31-rxp0-gbm.so|grep NEEDED
 0x0000000000000001 (NEEDED)             Shared library: [libpthread.so.0]
 0x0000000000000001 (NEEDED)             Shared library: [libdl.so.2]
 0x0000000000000001 (NEEDED)             Shared library: [librt.so.1]
 0x0000000000000001 (NEEDED)             Shared library: [libdrm.so.2]
 0x0000000000000001 (NEEDED)             Shared library: [libm.so.6]
 0x0000000000000001 (NEEDED)             Shared library: [libstdc++.so.6]
 0x0000000000000001 (NEEDED)             Shared library: [libgcc_s.so.1]
 0x0000000000000001 (NEEDED)             Shared library: [libc.so.6]

While at it, add a comment when dependencies are not met

Fixes:
 - No autobuilder failures (yet), found when debugging an issue with
   rockchip-mali and glslsandbox-player

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 5f1858e859833da272fce70bf445ca1b53ebffe1)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/rockchip-mali/Config.in

@@ -1,5 +1,6 @@
 config BR2_PACKAGE_ROCKCHIP_MALI
 	bool "rockchip-mali"
+	depends on BR2_INSTALL_LIBSTDCPP
 	depends on BR2_TOOLCHAIN_USES_GLIBC
 	depends on BR2_ARM_EABIHF || BR2_aarch64
 	# lidbrm. This would normally need a Config.in comment, but
@@ -30,3 +31,8 @@ config BR2_PACKAGE_PROVIDES_LIBGBM
 	default "rockchip-mali"
 
 endif
+
+comment "rockchip-mali needs a glibc toolchain w/ C++, threads"
+	depends on BR2_ARM_EABIHF || BR2_aarch64
+	depends on !BR2_INSTALL_LIBSTDCPP || \
+		!BR2_TOOLCHAIN_USES_GLIBC || !BR2_TOOLCHAIN_HAS_THREADS