sourceware.org: mirror urls (#15992)

sourceware.org is often quite overrun and times out or results in
certificate errors.

Since libffi, bzip2, elfutils, etc. are quite fundamental in
build chains, lets add some official mirrors.

libffi, bzip2, elfutils, lvm2, valgrind: add mirrors

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

@@ -6,18 +6,15 @@
 from spack import *
 
 
-class Libffi(AutotoolsPackage):
+class Libffi(AutotoolsPackage, SourcewarePackage):
     """The libffi library provides a portable, high level programming
     interface to various calling conventions. This allows a programmer
     to call any function specified by a call interface description at
     run time."""
     homepage = "https://sourceware.org/libffi/"
+    sourceware_mirror_path = "libffi/libffi-3.2.1.tar.gz"
 
-    # The server is sometimes a bit slow to respond
-    fetch_options = {'timeout': 60}
-
-    version('3.2.1', sha256='d06ebb8e1d9a22d19e38d63fdb83954253f39bedc5d46232a05645685722ca37',
-            url="https://sourceware.org/pub/libffi/libffi-3.2.1.tar.gz")
+    version('3.2.1', sha256='d06ebb8e1d9a22d19e38d63fdb83954253f39bedc5d46232a05645685722ca37')
 
     @property
     def headers(self):