cubelib, cubew: Add missing pkgconfig dependency (#10875)

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

@@ -15,6 +15,7 @@ class Cubelib(AutotoolsPackage):
     version('4.4.2', '843335c7d238493f1b4cb8e07555ccfe99a3fa521bf162e9d8eaa6733aa1f949')
     version('4.4',   'c903f3c44d3228ebefd00c831966988e')
 
+    depends_on('pkgconfig', type='build')
     depends_on('zlib')
 
     def url_for_version(self, version):

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

@@ -15,6 +15,7 @@ class Cubew(AutotoolsPackage):
     version('4.4.1', 'c09e3f5a3533ebedee2cc7dfaacd7bac4680c14c3fa540669466583a23f04b67')
     version('4.4',   'e9beb140719c2ad3d971e1efb99e0916')
 
+    depends_on('pkgconfig', type='build')
     depends_on('zlib')
 
     def url_for_version(self, version):