Adding pkg-config

packages/pkg_config.rb

 require 'package'
 
 class Pkg_config < Package
-  version '29.1'
-  source_url 'https://pkg-config.freedesktop.org/releases/pkg-config-0.29.1.tar.gz'
-  source_sha1 '271ce928f6d673cc16cbced2bfd14a5f2e5d3d37'
+  version '0.29.1'
+  source_url 'https://pkg-config.freedesktop.org/releases/pkg-config-0.29.1.tar.gz' # software source tarball url
+  source_sha1 '271ce928f6d673cc16cbced2bfd14a5f2e5d3d37'                     # source tarball sha1 sum
 
-  depends_on 'buildessential'
 
-  def self.build
-    system "configure --prefix=/usr/local --with-internal-glib --disable-host-tool"
-    system "make"
+  def self.build                                                  # self.build contains commands needed to build the software from source
+    system "./configure","--prefix=/usr/local","--with-internal-glib","--disable-host-tool"
+    system "make"                                                 # ordered chronologically
   end
 
-  def self.install
-    system "make  install"
-    #remove the man pages we couldn't install
+  def self.install                                                # self.install contains commands needed to install the software on the target system
+    system "make", "DESTDIR=#{CREW_DEST_DIR}", "install"          # remember to include DESTDIR set to CREW_DEST_DIR - needed to keep track of changes made to system
   end
 end