package/python-pybind: needs C++

python-pybind needs C++ since its addition in commit
f42f2a63b3c5733dc56a58b18d6ba417a59d8342:

-- Check for working CXX compiler: /usr/bin/c++ - broken
CMake Error at /nvmedata/autobuild/instance-24/output-1/host/share/cmake-3.18/Modules/CMakeTestCXXCompiler.cmake:59 (message):
  The C++ compiler

    "/usr/bin/c++"

  is not able to compile a simple test program.

Fixes:
 - http://autobuild.buildroot.org/results/90364b752bef3f7b4b1fd9181e21030349e0e529

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/python-pybind/Config.in

@@ -1,8 +1,12 @@
 config BR2_PACKAGE_PYTHON_PYBIND
 	bool "python-pybind"
+	depends on BR2_INSTALL_LIBSTDCPP
 	help
 	  PyBind is a lightweight header-only library that exposes C++
 	  types in Python and vice versa, mainly to create Python
 	  bindings of existing C++ code.
 
 	  http://pybind11.readthedocs.org/en/master
+
+comment "python-pybind needs a toolchain w/ C++"
+	depends on !BR2_INSTALL_LIBSTDCPP