Simplify compile flags

setup.py

@@ -4,12 +4,11 @@
 """
 from os import environ
 from pathlib import PurePosixPath
-from subprocess import STDOUT, check_output
 # Importing setuptools modifies the behaviour of setup from distutils
 # to support building wheels. It will be marked as unused by IDEs/static analysis.
 import setuptools
 import sys
-from typing import Sequence, Tuple
+from typing import Sequence
 
 from numpy.distutils.core import (Extension as FortranExtension, setup)
 from numpy.distutils.command.build_ext import build_ext as _build_ext
@@ -24,36 +23,26 @@ def create_fortran_extension(fq_name: str, sources: Sequence[str]) -> FortranExt
     :param sources: List of relative paths from this file to the sources
     :return: An Extension class to be built
     """
-    extra_compile_args, extra_link_args, extra_f90_compile_args = compiler_flags()
+    _remove_environment_compiler_flags()
     return FortranExtension(name=fq_name,
                             sources=sources,
-                            extra_f90_compile_args=extra_f90_compile_args,
-                            extra_link_args=extra_link_args,
-                            extra_compile_args=extra_compile_args)
+                            extra_f90_compile_args=["-O1", "-std=legacy"],
+                            extra_link_args=["-static", "-static-libgfortran", "-static-libgcc"]
+                                             if sys.platform == "win32" else [])
 
 
-def compiler_flags() -> Tuple[Sequence[str], Sequence[str]]:
+def _remove_environment_compiler_flags() -> None:
     """
-    :return: The compiler flags appropriate for this platform
+    Using the 'gfortran_linux-64' and 'gfortran_osx-64' conda packages gives poor fit results by default 
+    because they set several optimization compiler flags which alter the operation of the Fortran code. We 
+    must therefore remove these flags from the 'FFLAGS' environment variable before performing the compilation.
     """
-    extra_compile_args = []
-    extra_link_args = []
-    if sys.platform == "win32":
-        extra_link_args = ["-static", "-static-libgfortran", "-static-libgcc"]
-    elif sys.platform == "darwin":
-        extra_compile_args = ["-Wno-argument-mismatch"]
-        extra_link_args = ["-static", "-static-libgfortran", "-static-libgcc"]
-
     fflags_value = environ.get('FFLAGS')
     if isinstance(fflags_value, str):
         fflags_value = fflags_value.replace("-fstack-protector ", "")
         fflags_value = fflags_value.replace("-fstack-protector-strong ", "")
         environ['FFLAGS'] = fflags_value
 
-    extra_f90_compile_args = ["-O1", "-std=legacy"]
-
-    return extra_compile_args, extra_link_args, extra_f90_compile_args
-
 
 def source_paths(dirname: PurePosixPath, filenames: Sequence[str]) -> Sequence[str]:
     """