Don't build thread_utilization on windows

Author: TimPansino

setup.py

@@ -50,6 +50,7 @@
     raise RuntimeError(error_msg)
 
 with_setuptools = False
+is_windows = sys.platform == "win32"
 
 try:
     from setuptools import setup
@@ -89,7 +90,7 @@ def newrelic_agent_next_version(version):
 with readme_file.open() as f:
     readme_file_contents = f.read()
 
-if sys.platform == "win32" and python_version > (2, 6):
+if is_windows:
     build_ext_errors = (CCompilerError, DistutilsExecError, DistutilsPlatformError, IOError)
 else:
     build_ext_errors = (CCompilerError, DistutilsExecError, DistutilsPlatformError)
@@ -201,8 +202,13 @@ def _run_setup():
         if with_extensions:
             kwargs_tmp["ext_modules"] = [
                 Extension("newrelic.packages.wrapt._wrappers", ["newrelic/packages/wrapt/_wrappers.c"]),
-                Extension("newrelic.core._thread_utilization", ["newrelic/core/_thread_utilization.c"]),
             ]
+            if not is_windows:
+                # This extension is only supported on POSIX platforms.
+                kwargs_tmp["ext_modules"].append(
+                    Extension("newrelic.core._thread_utilization", ["newrelic/core/_thread_utilization.c"])
+                )
+
             kwargs_tmp["cmdclass"] = dict(build_ext=optional_build_ext)
 
         setup(**kwargs_tmp)