Dia needs access to gettext and pkg-config. (#8840)

When using spack on a ubuntu baseline system, I was unable to build dia with
adding these build dependencies on gettext and pkg-config.

var/spack/repos/builtin/packages/dia/package.py

@@ -33,6 +33,8 @@ class Dia(Package):
     version('0.97.3',    '0e744a0f6a6c4cb6a089e4d955392c3c')
 
     depends_on('intltool', type='build')
+    depends_on('gettext', type='build')
+    depends_on('pkg-config', type='build')
     depends_on('gtkplus@2.6.0:')
     depends_on('libxslt')
     depends_on('python')