Update to v0.12.0
    
    This update includes a major restructuring which breaks build2 into a library, libbuild2, and its bundled build module libraries, libbuild-{bash,bin,c,cc,cxx,in,version}. Thus, this also adds libbuild2{,-devel,-static} subpackages and moves some runtime requirements from build2 to the libbuild2 package.
    
     * .gitignore, build2.spec, sources: Update to v0.12.0
     * build2-libbuild2-buildfile-host_config-config.install.chroot-remove.patch: Upstream patch removing confit.install.chroot from libbuild2 host configuration. This prevents $RPM_BUILD_ROOT from appearing in libbuild2.