[CI] Remove redundant CIBW_BEFORE_BUILD (#631)

* The build system should define all required build components and
  make them available at wheel build time. As this pip install step
  is not required, remove CIBW_BEFORE_BUILD.

  From the docs https://cibuildwheel.pypa.io/en/stable/options/#before-build

  > If dependencies are required to build your wheel (for example if you
  > include a header from a Python module), instead of using this command,
  > we recommend adding requirements to a pyproject.toml file's
  > build-system.requires array instead.

Author: matthewfeickert

.github/workflows/build_wheels_weekly.yml

@@ -7,7 +7,7 @@ on:
   push:
     branches:
       - "master"
-      
+
 jobs:
   build_wheels:
     name: ${{ matrix.os }}
@@ -40,7 +40,6 @@ jobs:
     - name: Build wheels
       env:
         CIBW_SKIP: "pp*-win* pp*-macosx* cp2* pp* cp*musl* cp36* *i686" # remove pypy on mac and win (wrong version)
-        CIBW_BEFORE_BUILD: "pip install numpy cython"
         CIBW_ARCHS_LINUX: auto aarch64 # force aarch64 with QEMU
         CIBW_ARCHS_MACOS: x86_64 universal2 arm64
       run: |

Makefile

@@ -85,7 +85,7 @@ aautopep8 :
 	autopep8 -air test ot examples --jobs -1
 
 wheels :
-	CIBW_BEFORE_BUILD="pip install numpy cython" cibuildwheel --platform linux --output-dir dist
+	cibuildwheel --platform linux --output-dir dist
 
 dist : wheels
 	$(PYTHON) setup.py sdist