rpm: prefer the conditional %{?...} syntax

cmake/cpack_rpm.cmake

@@ -179,7 +179,7 @@ MACRO(ALTERNATIVE_NAME real alt)
   SET(p "CPACK_RPM_${real}_PACKAGE_PROVIDES")
   SET(${p} "${${p}} ${alt} = ${ver} ${alt}%{?_isa} = ${ver} config(${alt}) = ${ver}")
   SET(o "CPACK_RPM_${real}_PACKAGE_OBSOLETES")
-  SET(${o} "${${o}} ${alt} ${alt}%{_isa}")
+  SET(${o} "${${o}} ${alt} ${alt}%{?_isa}")
 ENDMACRO(ALTERNATIVE_NAME)
 
 ALTERNATIVE_NAME("devel"  "mysql-devel")