C++/Cpp Rakefile with includes, links... OpenCV example

Rakefile

#
# CPP Rakefile
#
EXEC  = "square"            # Your app executable
FLAGS = "-Wall -Wextra"     # Flags for building
EXTRA = %w{ OpenCV }        # Extra includes

#
# Nothing to see here, move along...
#
COMPILER = "g++"

# Compilation (add flags as needed)
CXXFLAGS = EXTRA.map { |e| `pkg-config #{e.downcase} --cflags` }.join.chomp

# Linking (add flags as needed)
LDFLAGS  = EXTRA.map { |e| `pkg-config #{e.downcase} --libs` }.join.chomp

C_FILES    ||= Dir.glob("./*.c")
CPP_FILES  ||= Dir.glob("./*.cpp")

BUILD_OUTPUT     ||= 'build'

def build_output_path(file)
  Dir.mkdir(BUILD_OUTPUT) if Dir.exist?(BUILD_OUTPUT) == false
  File.join(BUILD_OUTPUT, file)
end

desc "Running unit tests"
task :spec do
end

task :c do
  C_FILES.each do |source|
  end
end

task :cpp do
  CPP_FILES.each do |source|
    output = build_output_path(File.basename(source, File.extname(source)) + ".o")
    sh "#{COMPILER} #{FLAGS} #{CXXFLAGS} -c -o #{output} #{source}"
  end
end

task :link do
  os = CPP_FILES.map { |f| BUILD_OUTPUT + f[1..-1][0...-3] + "o" }
  sh "#{COMPILER} #{FLAGS} #{LDFLAGS} #{os.join(" ")} -o #{EXEC}"
end

desc "Clean stuff"
task :clean do
  files = (Dir["#{EXEC}"] + Dir[BUILD_OUTPUT]).uniq
  rm_rf files unless files.empty?
end

desc "Compile App"
task :compile => [:c, :cpp, :link]
task :default => [:compile]