Added support for configuration data in exporters

This commit integrates configuration data with exporters, in a similar
way to the integration in build_project or build_library in
tools/build_api.py.

Only a very simple test was done for this PR: define a configuration
parameter in the mbed_app.json of a blinky example, export it to uvision
and check if the corresponding macro made it into the project file. If
there are better tests to be performed, please let me know.

Author: Bogdan Marinescu

tools/export/exporters.py

@@ -17,6 +17,8 @@
 from project_generator.project import Project
 from project_generator.settings import ProjectSettings
 
+from tools.config import Config
+
 class OldLibrariesException(Exception): pass
 
 class Exporter(object):
@@ -32,6 +34,7 @@ def __init__(self, target, inputDir, program_name, build_url_resolver, extra_sym
         jinja_loader = FileSystemLoader(os.path.dirname(os.path.abspath(__file__)))
         self.jinja_environment = Environment(loader=jinja_loader)
         self.extra_symbols = extra_symbols
+        self.config_macros = []
 
     def get_toolchain(self):
         return self.TOOLCHAIN
@@ -115,6 +118,8 @@ def __scan_all(self, path):
     def scan_and_copy_resources(self, prj_paths, trg_path, relative=False):
         # Copy only the file for the required target and toolchain
         lib_builds = []
+        # Create the configuration object
+        cfg = Config(self.target, prj_paths)
         for src in ['lib', 'src']:
             resources = reduce(add, [self.__scan_and_copy(join(path, src), trg_path) for path in prj_paths])
             lib_builds.extend(resources.lib_builds)
@@ -145,6 +150,10 @@ def scan_and_copy_resources(self, prj_paths, trg_path, relative=False):
         else:
             # use the prj_dir (source, not destination)
             self.resources = reduce(add, [self.toolchain.scan_resources(path) for path in prj_paths])
+        # Add all JSON files discovered during scanning to the configuration object
+        cfg.add_config_files(self.resources.json_files)
+        # Get data from the configuration system
+        self.config_macros = cfg.get_config_data_macros()
         # Check the existence of a binary build of the mbed library for the desired target
         # This prevents exporting the mbed libraries from source
         # if not self.toolchain.mbed_libs:
@@ -163,7 +172,7 @@ def get_symbols(self, add_extra_symbols=True):
         """ This function returns symbols which must be exported.
             Please add / overwrite symbols in each exporter separately
         """
-        symbols = self.toolchain.get_symbols()
+        symbols = self.toolchain.get_symbols() + self.config_macros
         # We have extra symbols from e.g. libraries, we want to have them also added to export
         if add_extra_symbols:
             if self.extra_symbols is not None: