lighttpd : fix pcre depends (#15168)

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

@@ -21,5 +21,7 @@ class Lighttpd(CMakePackage):
     version('1.4.50', sha256='c9a9f175aca6db22ebebbc47de52c54a99bbd1dce8d61bb75103609a3d798235')
     version('1.4.49', sha256='8b744baf9f29c386fff1a6d2e435491e726cb8d29cfdb1fe20ab782ee2fc2ac7')
 
+    depends_on('pcre')
+
     def cmake_args(self):
         return ["-DSBINDIR=bin"]