Automatically add source directory to "CPPPATH" of Build System

HISTORY.rst

@@ -9,6 +9,7 @@ PlatformIO 2.0
 
 * Simplified documentation for `Continuous Integration with AppVeyor <http://docs.platformio.org/en/latest/ci/appveyor.html>`__
   (`issue #671 <https://github.com/platformio/platformio/issues/671>`_)
+* Automatically add source directory to ``CPPPATH`` of Build System
 * Added support for Silicon Labs SLSTK3401A (Pearl Gecko) and
   MultiTech mDot F411 ARM mbed based boards
 * Added support for MightyCore ATmega8535 board

platformio/builder/tools/platformio.py

@@ -80,6 +80,7 @@ def BuildProgram(env):
     env.Append(
         CPPDEFINES=["PLATFORMIO={0:02d}{1:02d}{2:02d}".format(
             *pioversion_to_intstr())],
+        CPPPATH=["$PROJECTSRC_DIR"],
         LIBS=deplibs,
         LIBPATH=["$BUILD_DIR"]
     )