Adding back -march=native for non-wheel builds.

This way, when installing from source (either via a local
checkout or from the source dist on PyPI) the most optimal machine
instructions will be produced.

Fixed #99.

scripts/manylinux/build-wheels.sh

@@ -40,6 +40,9 @@ for PYBIN in /opt/python/*/bin; do
     fi
 done
 
+# Indicate that wheels are being built.
+export BEZIER_WHEEL=True
+
 # Compile wheels
 for PYBIN in ${VERSION_WHITELIST}; do
     "${PYBIN}/pip" install -r /io/scripts/manylinux/dev-requirements.txt

scripts/osx/build-wheels.sh

@@ -54,6 +54,9 @@ ${PY_BIN} -m pip install --upgrade setuptools numpy
 # Make sure the custom ``libgfortran`` is in place.
 ${PY_BIN} ${OSX_DIR}/make_universal_libgfortran.py
 
+# Indicate that wheels are being built.
+export BEZIER_WHEEL=True
+
 # Create the wheel (make sure to use the custom ``libgfortran``).
 DIST_WHEELS="${OSX_DIR}/dist_wheels"
 mkdir -p ${DIST_WHEELS}

setup_helpers.py

@@ -35,6 +35,12 @@
 ``scripts/osx/make_universal_libgfortran.py`` and
 ``scripts/osx/build-wheels.sh`` for an example of this.)
 """
+WHEEL_ENV = "BEZIER_WHEEL"
+"""Environment variable used to indicate a wheel is being built.
+
+If this is present (e.g. ``BEZIER_WHEEL="True"``) then the ``-march=native``
+flag will **not** be used.
+"""
 FORTRAN_LIBRARY_PREFIX = "libraries: ="
 GFORTRAN_MISSING_LIBS = (
     """\
@@ -62,6 +68,7 @@
 GFORTRAN_DEBUG_FLAGS = (
     "-g", "-fcheck=all", "-fbacktrace", "-fimplicit-none", "-pedantic"
 )
+GFORTRAN_NATIVE_FLAG = "-march=native"
 GFORTRAN_OPTIMIZE_FLAGS = ("-Werror", "-O3", "-funroll-loops")
 BAD_JOURNAL = "Saving journal failed with {!r}."
 JOURNAL_ENV = "BEZIER_JOURNAL"
@@ -234,6 +241,8 @@ def patch_f90_compiler(f90_compiler):
         to_remove = GFORTRAN_OPTIMIZE_FLAGS
     else:
         to_add = GFORTRAN_OPTIMIZE_FLAGS
+        if os.environ.get(WHEEL_ENV) is None:
+            to_add += (GFORTRAN_NATIVE_FLAG,)
         to_remove = GFORTRAN_DEBUG_FLAGS
     for flag in to_add:
         if flag not in f90_flags: