def build_after(targets, prerequisites)
      targets = Array(targets)
      prerequisites = Array(prerequisites)
      targets.each do |target|
        target = expand_path(expand_varref(target))
        @registered_build_dependencies[target] ||= Set.new
        prerequisites.each do |prerequisite|
          prerequisite = expand_path(expand_varref(prerequisite))
          @registered_build_dependencies[target] << prerequisite
        end
      end
    end
def build_after(targets, prerequisites)
      targets = Array(targets)
      prerequisites = Array(prerequisites)
      targets.each do |target|
        target = expand_path(expand_varref(target))
        @registered_build_dependencies[target] ||= Set.new
        prerequisites.each do |prerequisite|
          prerequisite = expand_path(expand_varref(prerequisite))
          @registered_build_dependencies[target] << prerequisite
        end
      end
    end
Manually record the given target(s) as needing to be built after the
 given prerequisite(s).

 For example, consider a builder registered to generate gen.c which also
 generates gen.h as a side-effect. If program.c includes gen.h, then it
 should not be compiled before gen.h has been generated. When using
 multiple threads to build, Rscons may attempt to compile program.c before
 gen.h has been generated because it does not know that gen.h will be
 generated along with gen.c. One way to prevent that situation would be
 to first process the Environment with just the code-generation builders
 in place and then register the compilation builders. Another way is to
 use this method to record that a certain target should not be built until
 another has completed. For example, for the situation previously
 described:
   env.build_after("program.o", "gen.c")

 @since 1.10.0

 @param targets [String, Array<String>]
   Target files to wait to build until the prerequisites are finished
   building.
 @param prerequisites [String, Array<String>]
   Files that must be built before building the specified targets.

 @return [void]