Add dependencies to make sure pkgconfig is installed prior to any source code

compilations.  This solves the easy-to-forget-pkgconfig-who-do-not-use-x86_64
problem.

packages/buildessential.rb

@@ -8,4 +8,5 @@ class Buildessential < Package
   depends_on 'gcc'
   depends_on 'make'
   depends_on 'linuxheaders'
+  depends_on 'pkgconfig'
 end

packages/pkgconfig.rb

@@ -5,7 +5,12 @@ class Pkgconfig < Package
   source_url 'http://pkgconfig.freedesktop.org/releases/pkg-config-0.29.1.tar.gz'
   source_sha1 '271ce928f6d673cc16cbced2bfd14a5f2e5d3d37'
 
-  depends_on 'buildessential'
+  # It is not possible to write buildessential here since it depends on build essential too.
+  #   depends_on 'buildessential'
+  # Write dependency to gcc make linuxheaders instead.
+  depends_on 'gcc'
+  depends_on 'make'
+  depends_on 'linuxheaders'
 
   def self.build
       # check lib64 on any architectures since it is not a problem to not exist lib64 directory.