Fixed an issue when configuration file options partly ignored when `--project-conf` // Resolve #3034 (#3055)

* Fixed an issue when configuration file options partly ignored when using custom ``--project-conf`` // Resolve #3034

* Py2 compatible makedirs

* Fix circle dependency

* Fix broken import in test examples

* Fix history

* Remove YAPF markers

* PyLint fix

* Fix invalid project conf path

* Move PIO Core to the root on Windows, issue with long CPPPATHs

* Respect global PLATFORMIO_BUILD_CACHE_DIR env var

* Fix Appveyor paths

* Minor changes

platformio/check/tools/cppcheck.py

@@ -19,7 +19,6 @@ from tempfile import NamedTemporaryFile
 from platformio.check.defect import DefectItem
 from platformio.check.tools.base import CheckToolBase
 from platformio.managers.core import get_core_package_dir
-from platformio.project.helpers import get_project_core_dir
 
 
 class CppcheckCheckTool(CheckToolBase):
@@ -110,7 +109,7 @@ class CppcheckCheckTool(CheckToolBase):
         cmd.append("--file-list=%s" % self._generate_src_file())
         cmd.append("--includes-file=%s" % self._generate_inc_file())
 
-        core_dir = get_project_core_dir()
+        core_dir = self.config.get_optional_dir("core")
         cmd.append("--suppress=*:%s*" % core_dir)
         cmd.append("--suppress=unmatchedSuppression:%s*" % core_dir)