Add CPython 3.7.0a1

plugins/python-build/share/python-build/3.7.0a1

@@ -0,0 +1,8 @@
+#require_gcc
+install_package "openssl-1.0.2k" "https://www.openssl.org/source/openssl-1.0.2k.tar.gz#6b3977c61f2aedf0f96367dcfb5c6e578cf37e7b8d913b4ecb6643c3cb88d8c0" mac_openssl --if has_broken_mac_openssl
+install_package "readline-6.3" "https://ftpmirror.gnu.org/readline/readline-6.3.tar.gz#56ba6071b9462f980c5a72ab0023893b65ba6debb4eeb475d7a563dc65cafd43" standard --if has_broken_mac_readline
+if has_tar_xz_support; then
+  install_package "Python-3.7.0a1" "https://www.python.org/ftp/python/3.7.0/Python-3.7.0a1.tar.xz#aab053dc3c23b829c60e973ce5972c4e58ffb5e26210acc26611e0d766a06eea" ldflags_dirs standard verify_py37 ensurepip
+else
+  install_package "Python-3.7.0a1" "https://www.python.org/ftp/python/3.7.0/Python-3.7.0a1.tgz#8704820e98acb8b6c659b9c82b010b73f92e78e9a898c10786ab0ccb9defe2b0" ldflags_dirs standard verify_py37 ensurepip
+fi