dev-python/cryptography: append -pthread to CFLAGS

This works around some weird distutils behavior when CC is set in the
environment.

Bug: https://bugs.gentoo.org/630578
Package-Manager: Portage-2.3.11_p4, Repoman-2.3.3_p62

dev-python/cryptography/cryptography-2.0.3.ebuild

@@ -6,7 +6,7 @@ EAPI=6
 PYTHON_COMPAT=( python2_7 python3_{4,5,6} pypy{,3} )
 PYTHON_REQ_USE="threads(+)"
 
-inherit distutils-r1
+inherit distutils-r1 flag-o-matic
 
 DESCRIPTION="Library providing cryptographic recipes and primitives"
 HOMEPAGE="https://github.com/pyca/cryptography/ https://pypi.python.org/pypi/cryptography/"
@@ -42,6 +42,10 @@ DEPEND="${RDEPEND}
 
 DOCS=( AUTHORS.rst CONTRIBUTING.rst README.rst )
 
+python_configure_all() {
+	append-cflags $(test-flags-CC -pthread)
+}
+
 python_test() {
 	py.test -v -v -x || die "Tests fail with ${EPYTHON}"
 }