Fixing build workflow (#1212)

* improve pip and local installation. Remove statement about outdated fast-pt

.github/environment.yml

@@ -10,8 +10,7 @@ dependencies:
   - swig
   - pyyaml
   - numpy<2
-  # The below is only because the current version of fast-pt uses deprecated scipy functions.
-  # DarkEmulator also uses an old scipy.
+  # The below is only because the current version of DarkEmulator uses deprecated scipy functions.
   # We should remove the <1.14 flag as soon as this is fixed.
   - scipy<1.14
   - camb

.github/workflows/ci.yml

@@ -91,7 +91,7 @@ jobs:
           pip install --no-build-isolation classy==2.9.4
 
       - name: Install CCL
-        run: pip install --no-use-pep517 -v -e .
+        run: pip install -v -e .
 
       - name: Unit tests
         run: |

pyproject.toml

@@ -1,5 +1,6 @@
 [build-system]
-requires = ["setuptools>=64", "setuptools_scm>=8", "cmake", "swig"]
+requires = ["setuptools>=64", "setuptools_scm>=8", "cmake", "swig", "numpy"]
+build-backend = "setuptools.build_meta"
 
 [project]
 name = "pyccl"