Fix IntelliSense in VSCode export

Allow to use default intelliSenseEngine in visual studio code.
Add of compilerPath and forcedInclude of mbed_config header in the
created c_cpp_properties.json file.

Author: ngraziano

tools/export/vscode/__init__.py

@@ -67,16 +67,29 @@ def generate(self):
             "configurations": [
                 {
                     "name": "Windows",
+                    "forcedInclude": [
+                        "${workspaceRoot}\\mbed_config.h"
+                    ],
+                    "compilerPath": self.toolchain.cppc[0],
+                    "intelliSenseMode": "gcc-x64",
                     "includePath": [x.replace("/", "\\") for x in all_directories],
                     "defines": [symbol for symbol in self.toolchain.get_symbols()]
                 },
                 {
                     "name": "Mac",
+                    "forcedInclude": [
+                        "${workspaceRoot}\\mbed_config.h"
+                    ],
+                    "compilerPath": self.toolchain.cppc[0],
                     "includePath": all_directories,
                     "defines": [symbol for symbol in self.toolchain.get_symbols()]
                 },
                 {
                     "name": "Linux",
+                    "forcedInclude": [
+                        "${workspaceRoot}\\mbed_config.h"
+                    ],
+                    "compilerPath": self.toolchain.cppc[0],
                     "includePath": all_directories,
                     "defines": [symbol for symbol in self.toolchain.get_symbols()]
                 }