Installing conf-openblas 0.2.1 needs PKG_CONFIG_PATH extended.

[tmcgilchrist]

Installing the conf-openblas package on macOS Sonoma ARM fails with:

#=== ERROR while compiling conf-openblas.0.2.1 ================================#
# context     2.1.5 | macos/arm64 | ocaml-base-compiler.5.0.0 | https://opam.ocaml.org#7600b9b6
# path        ~/code/ocaml/par-matmul-profiling/_opam/.opam-switch/build/conf-openblas.0.2.1
# command     ~/.opam/opam-init/hooks/sandbox.sh build sh -exc cc $CFLAGS $(pkg-config --cflags openblas) test.c $(pkg-config --libs openblas)
# exit-code   1
# env-file    ~/.opam/log/conf-openblas-60410-e8868b.env
# output-file ~/.opam/log/conf-openblas-60410-e8868b.out
### output ###
# [...]
# to the PKG_CONFIG_PATH environment variable
# No package 'openblas' found
# ++ pkg-config --libs openblas
# Package openblas was not found in the pkg-config search path.
# Perhaps you should add the directory containing `openblas.pc'
# to the PKG_CONFIG_PATH environment variable
# No package 'openblas' found
# + cc test.c
# test.c:2:10: fatal error: 'cblas.h' file not found
# #include <cblas.h>
#          ^~~~~~~~~
# 1 error generated.



<><> Error report <><><><><><><><><><><><><><><><><><><><><><><><><><><><><>  🐫 
┌─ The following actions failed
│ λ build conf-openblas 0.2.1
└─ 

Installing openblas via brew suggests setting export PKG_CONFIG_PATH="/opt/homebrew/opt/openblas/lib/pkgconfig" to get pkg-config --cflags openblas to work correctly. Running this manually works and correctly installs the package.

What is the recommended way to set PKG_CONFIG_PATH for this package?