DOC: update code comment about NPY_USE_BLAS_ILP64 environment variable (numpy#24289)

As suggested by Chuck in a review comment on a previous PR. Sending as a
separate follow-up also because it helps to check Cirrus CI triggering
which we are looking at in issue 24280.

[skip azp] [skip circle] [skip actions] [skip travis]

Author: rgommers

numpy/meson.build

@@ -55,8 +55,9 @@ blas_symbol_suffix = get_option('blas-symbol-suffix')
 
 use_ilp64 = get_option('use-ilp64')
 if not use_ilp64
-  # For now, keep supporting this environment variable too (same as in setup.py)
-  # `false is the default for the CLI flag, so check if env var was set
+  # For now, keep supporting the `NPY_USE_BLAS_ILP64` environment variable too
+  # (same as in setup.py) `false is the default for the CLI flag, so check if
+  # env var was set
   use_ilp64 = run_command(py,
     [
       '-c',