add BuildRequires: gcc-c++

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

neon.spec

@@ -11,6 +11,7 @@ Source0: http://www.webdav.org/neon/neon-%{version}.tar.gz
 Patch0: neon-0.27.0-multilib.patch
 Patch1: neon-0.30.2-sysuioh.patch
 Patch2: neon-0.30.2-lockprintf.patch
+BuildRequires:  gcc-c++
 BuildRequires: expat-devel, openssl-devel, zlib-devel, krb5-devel, libproxy-devel
 BuildRequires: pkgconfig, pakchois-devel
 Requires: ca-certificates