BLD: enable building NumPy with Meson

This enables building with NumPy on Linux and macOS. Windows support
should be complete to, but is untested as of now and may need a few
tweaks. This contains:
- A set of `meson.build` files and related code generation script
  tweaks, header templates, etc.
- One CI job on Linux
- Basic docs on using Meson to build NumPy (not yet integrated in the
  html docs, it's too early for that - this is for early adopters right
  now).

The build should be complete, with the major exception of SIMD support.
The full test suite passes. See gh-22546 for the tracking issue with
detailed notes on the plan for switching NumPy to Meson as its build
system.

Co-authored-by: Stefan van der Walt <stefanv@berkeley.edu>

1 files changed, 6 insertions, 0 deletions

diff --git a/numpy/core/setup.py b/numpy/core/setup.py
index 10b8c093e..6f0a4417a 100644
--- a/numpy/core/setup.py
+++ b/numpy/core/setup.py
@@ -45,6 +45,8 @@ NPY_DISABLE_SVML = (os.environ.get('NPY_DISABLE_SVML', "0") == "1")
 # in time is only in build. -- Charles Harris, 2013-03-30
 
 class CallOnceOnly:
+    # NOTE: we don't need any of this in the Meson build,
+    # it takes care of caching
     def __init__(self):
         self._check_types = None
         self._check_ieee_macros = None
@@ -177,6 +179,8 @@ def check_math_capabilities(config, ext, moredefs, mathlibs):
         else:
             return 1
 
+    # NOTE: not needed in Meson build, we set the minimum
+    #       compiler version to 8.4 to avoid this bug
     # GH-14787: Work around GCC<8.4 bug when compiling with AVX512
     # support on Windows-based platforms
     def check_gh14787(fn):
@@ -427,6 +431,8 @@ def check_types(config_cmd, ext, build_dir):
 
     return private_defines, public_defines
 
+# NOTE: this isn't needed in the Meson build,
+#       and we won't support a MATHLIB env var
 def check_mathlib(config_cmd):
     # Testing the C math library
     mathlibs = []