M1 MacでScipyが入らないときにやったこと

M1 Macでpyenv環境を作成してもろもろライブラリをインストールしようとしたところ、scipyが入らない。
scipyが入らないとscikit-learnが入らないので致命的。
※ pyenvではpythonバージョンを3.9.16としている

# エラーメッセージ
```xxxxxxxxxxxxxxxxxxx ~ % pip install scipy
Collecting scipy
  Using cached scipy-1.10.1.tar.gz (42.4 MB)
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
  Installing backend dependencies ... done
  Preparing metadata (pyproject.toml) ... error
  error: subprocess-exited-with-error

  × Preparing metadata (pyproject.toml) did not run successfully.
  │ exit code: 1
  ╰─> [40 lines of output]
      The Meson build system
      Version: 1.1.0
      Source dir: /private/var/folders/5_/kwy7fv5j6n1_4jsf8xmgtdkr0000gn/T/pip-install-butlt1cb/scipy_4e7a7a2084554d13b7700b0a3e7a5b7e
      Build dir: /private/var/folders/5_/kwy7fv5j6n1_4jsf8xmgtdkr0000gn/T/pip-install-butlt1cb/scipy_4e7a7a2084554d13b7700b0a3e7a5b7e/.mesonpy-8f_j0aem/build
      Build type: native build
      Project name: SciPy
      Project version: 1.10.1
      C compiler for the host machine: cc (clang 12.0.5 "Apple clang version 12.0.5 (clang-1205.0.22.11)")
      C linker for the host machine: cc ld64 650.9
      C++ compiler for the host machine: c++ (clang 12.0.5 "Apple clang version 12.0.5 (clang-1205.0.22.11)")
      C++ linker for the host machine: c++ ld64 650.9
      Cython compiler for the host machine: cython (cython 0.29.35)
      Host machine cpu family: aarch64
      Host machine cpu: aarch64
      Compiler for C supports arguments -Wno-unused-but-set-variable: NO
      Compiler for C supports arguments -Wno-unused-function: YES
      Compiler for C supports arguments -Wno-conversion: YES
      Compiler for C supports arguments -Wno-misleading-indentation: YES
      Compiler for C supports arguments -Wno-incompatible-pointer-types: YES
      Library m found: YES
      Fortran compiler for the host machine: gfortran (gcc 13.1.0 "GNU Fortran (Homebrew GCC 13.1.0) 13.1.0")
      Fortran linker for the host machine: gfortran ld64 650.9
      Compiler for Fortran supports arguments -Wno-conversion: YES
      Checking if "-Wl,--version-script" : links: NO
      Program cython found: YES (/private/var/folders/5_/kwy7fv5j6n1_4jsf8xmgtdkr0000gn/T/pip-build-env-m33zcgb8/overlay/bin/cython)
      Program python found: YES (/Users/<username>/.pyenv/versions/3.9.16/bin/python3.9)
      Found pkg-config: /opt/homebrew/bin/pkg-config (0.29.2)
      Program pythran found: YES (/private/var/folders/5_/kwy7fv5j6n1_4jsf8xmgtdkr0000gn/T/pip-build-env-m33zcgb8/overlay/bin/pythran)
      Run-time dependency threads found: YES
      Library npymath found: YES
      Library npyrandom found: YES
      Found CMake: /opt/homebrew/bin/cmake (3.26.4)
      WARNING: CMake Toolchain: Failed to determine CMake compilers state
      Run-time dependency openblas found: NO (tried pkgconfig, framework and cmake)
      Run-time dependency openblas found: NO (tried pkgconfig, framework and cmake)

      ../../scipy/meson.build:134:7: ERROR: Dependency "OpenBLAS" not found, tried pkgconfig, framework and cmake

      A full log can be found at /private/var/folders/5_/kwy7fv5j6n1_4jsf8xmgtdkr0000gn/T/pip-install-butlt1cb/scipy_4e7a7a2084554d13b7700b0a3e7a5b7e/.mesonpy-8f_j0aem/build/meson-logs/meson-log.txt
      + meson setup --prefix=/Users/<username>/.pyenv/versions/3.9.16 /private/var/folders/5_/kwy7fv5j6n1_4jsf8xmgtdkr0000gn/T/pip-install-butlt1cb/scipy_4e7a7a2084554d13b7700b0a3e7a5b7e /private/var/folders/5_/kwy7fv5j6n1_4jsf8xmgtdkr0000gn/T/pip-install-butlt1cb/scipy_4e7a7a2084554d13b7700b0a3e7a5b7e/.mesonpy-8f_j0aem/build --native-file=/private/var/folders/5_/kwy7fv5j6n1_4jsf8xmgtdkr0000gn/T/pip-install-butlt1cb/scipy_4e7a7a2084554d13b7700b0a3e7a5b7e/.mesonpy-native-file.ini -Ddebug=false -Doptimization=2
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.
```

# 解決策
1. homebrewでOpenBLASインストール
1. ほか必要ライブラリをインストール
1. 環境変数を指定してscipy v1.7.0をpip install

```
brew install openblas
pip install cython pybind11 pythran numpy
OPENBLAS=$(brew --prefix openblas) CFLAGS="-falign-functions=8 ${CFLAGS}" pip install --no-use-pep517 scipy==1.7.0
```
参考：https://github.com/scipy/scipy/issues/13409#issue-790703815