Fix issues with build command.

The extension was not properly build with the “python setup.py install” command, it worked fine with “python setup.py build” but the building wasn’t executed when invoking “install” directly.

setup.py

@@ -14,7 +14,7 @@
 # limitations under the License.
 #
 
-from distutils.command.build import build
+from distutils.command.build_ext import build_ext
 from setuptools import setup, Command, Extension
 from codecs import open
 
@@ -66,26 +66,28 @@ def has_function(function_name, libraries=None):
   return result
 
 
-class BuildCommand(build):
+class BuildCommand(build_ext):
 
-  user_options = build.user_options + [
+  user_options = build_ext.user_options + [
       ('dynamic-linking', None,'link dynamically against libyara'),
       ('enable-cuckoo', None,'enable "cuckoo" module'),
       ('enable-magic', None,'enable "magic" module'),
       ('enable-profiling', None,'enable profiling features')]
 
-  boolean_options = build.boolean_options + [
+  boolean_options = build_ext.boolean_options + [
       'dynamic-linking', 'enable-cuckoo', 'enable-magic', 'enable-profiling']
 
   def initialize_options(self):
-    build.initialize_options(self)
+
+    build_ext.initialize_options(self)
     self.dynamic_linking = None
     self.enable_magic = None
     self.enable_cuckoo = None
     self.enable_profiling = None
 
   def finalize_options(self):
-    build.finalize_options(self)
+
+    build_ext.finalize_options(self)
     if self.enable_magic and self.dynamic_linking:
       raise distutils.errors.DistutilsOptionError(
           '--enable-magic can''t be used with --dynamic-linking')
@@ -102,7 +104,7 @@ class BuildCommand(build):
     if base_dir:
       os.chdir(base_dir)
 
-    exclusions = ['yara/libyara/modules/pe_utils.c']
+    exclusions = []
 
     if self.plat_name in ('win32','win-amd64'):
       building_for_windows = True
@@ -169,7 +171,7 @@ class BuildCommand(build):
           if x.endswith('.c') and x not in exclusions:
             module.sources.append(x)
 
-    build.run(self)
+    build_ext.run(self)
 
 
 class UpdateCommand(Command):
@@ -219,7 +221,7 @@ setup(
     url='https://github.com/VirusTotal/yara-python',
     zip_safe=False,
     cmdclass={
-        'build': BuildCommand,
+        'build_ext': BuildCommand,
         'update': UpdateCommand},
     ext_modules=[Extension(
         name='yara',