DEP: doc-deprecate BLAS_SRC/LAPACK_SRC

Building BLAS and LAPACK from sources in a NumPy build makes
very little sense in 2021. Therefore remove the documentation
for this from `site.cfg.example`, and doc-deprecate it in
`distutils/system_info.py`.

It's hard to properly deprecate and not worth doing, just
de-emphasizing is enough.

[ci skip]

1 files changed, 1 insertions, 10 deletions

diff --git a/site.cfg.example b/site.cfg.example
index c809303a2..1a6b36d2c 100644
--- a/site.cfg.example
+++ b/site.cfg.example
@@ -28,7 +28,7 @@
 #       extensions with this dependency. Use the character given by os.pathsep
 #       to separate the items in the list. Note that this character is known to
 #       vary on some unix-like systems; if a colon does not work, try a comma.
-#       This also applies to include_dirs and src_dirs (see below).
+#       This also applies to include_dirs.
 #       On UN*X-type systems (OS X, most BSD and Linux systems):
 #           library_dirs = /usr/lib:/usr/local/lib
 #       On Windows:
@@ -40,15 +40,6 @@
 #       List of directories to add to the header file search path.
 #           include_dirs = /usr/include:/usr/local/include
 #
-#   src_dirs
-#       List of directories that contain extracted source code for the
-#       dependency. For some dependencies, numpy.distutils will be able to build
-#       them from source if binaries cannot be found. The FORTRAN BLAS and
-#       LAPACK libraries are one example. However, most dependencies are more
-#       complicated and require actual installation that you need to do
-#       yourself.
-#           src_dirs = /home/username/src/BLAS_SRC:/home/username/src/LAPACK_SRC
-#
 #   search_static_first
 #       Boolean (one of (0, false, no, off) for False or (1, true, yes, on) for
 #       True) to tell numpy.distutils to prefer static libraries (.a) over