add BuildRequires: gcc

Reference: https://fedoraproject.org/wiki/Changes/Remove_GCC_from_BuildRoot

python-msgpack.spec

@@ -15,6 +15,7 @@ License:        ASL 2.0
 URL:            https://pypi.python.org/pypi/msgpack-python/
 Source0:        https://files.pythonhosted.org/packages/source/m/%{srcname}-python/%{srcname}-python-%{version}.tar.gz
 
+BuildRequires:  gcc
 BuildRequires:  Cython
 BuildRequires:  python2-devel
 BuildRequires:  python2-setuptools