MNT: Add meson-python, numpy, pybind11 and setuptools-scm in

     requirements/doc/doc-requirements.txt
    * Update the CI build files to refer to the requirments file rather than
      installing dependencies manually

.circleci/config.yml

@@ -103,7 +103,7 @@ commands:
       - run:
           name: Install Python dependencies
           command: |
-            python -m pip install --user meson-python numpy pybind11 setuptools-scm
+            python -m pip install --user ".[build]"
             python -m pip install --user \
                 numpy<< parameters.numpy_version >> \
                 -r requirements/doc/doc-requirements.txt

azure-pipelines.yml

@@ -135,7 +135,7 @@ stages:
 
           - bash: |
               python -m pip install --upgrade pip
-              python -m pip install --upgrade meson-python numpy pybind11 setuptools-scm
+              python -m pip install --upgrade ".[build]"
               python -m pip install -r requirements/testing/all.txt -r requirements/testing/extra.txt
             displayName: 'Install dependencies with pip'
 

requirements/dev/dev-requirements.txt

@@ -1,3 +1,4 @@
+-r ../build/build-requirements.txt
 -r ../doc/doc-requirements.txt
 -r ../testing/all.txt
 -r ../testing/extra.txt