Used hardcoded, downloadable scons for C++ tut

tutorials/plugins/gdnative/files/cpp_example/SConstruct

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+#!python
+import os
+
+target = ARGUMENTS.get("target", "debug")
+platform = ARGUMENTS.get("platform", "windows")
+bits = ARGUMENTS.get("bits", 64)
+
+final_lib_path = 'demo/bin/'
+
+# This makes sure to keep the session environment variables on windows, 
+# that way you can run scons in a vs 2017 prompt and it will find all the required tools
+env = Environment()
+if platform == "windows":
+    env = Environment(ENV = os.environ)
+
+def add_sources(sources, directory):
+    for file in os.listdir(directory):
+        if file.endswith('.cpp'):
+            sources.append(directory + '/' + file)
+
+if platform == "osx":
+    env.Append(CCFLAGS = ['-g','-O3', '-arch', 'x86_64'])
+    env.Append(LINKFLAGS = ['-arch', 'x86_64'])
+
+    final_lib_path = final_lib_path + 'osx/'
+
+elif platform == "linux":
+    env.Append(CCFLAGS = ['-fPIC', '-g','-O3', '-std=c++14'])
+
+    final_lib_path = final_lib_path + 'x11/'
+
+elif platform == "windows":
+    if target == "debug":
+        env.Append(CCFLAGS = ['-EHsc', '-D_DEBUG', '-MDd'])
+    else:
+        env.Append(CCFLAGS = ['-O2', '-EHsc', '-DNDEBUG', '-MD'])
+
+    final_lib_path = final_lib_path + 'win' + str(bits) + '/'
+
+env.Append(CPPPATH=['.', 'src/', "godot_headers/", 'godot-cpp/include/', 'godot-cpp/include/core/'])
+env.Append(LIBS=["godot-cpp/bin/godot-cpp" + "." + platform + "." + str(bits)])
+
+sources = []
+add_sources(sources, "src")
+
+library = env.SharedLibrary(target=final_lib_path + 'libgdexample', source=sources)
+Default(library)