Configure ReadTheDocs

Provides the necessary configuration files and settings to build on
ReadTheDocs. Requires a hack to the build system to handle the toolchain
configuration in the ReadTheDocs environment. Otherwise everything else
is pretty standard.

environment_doc.yml

@@ -0,0 +1,12 @@
+name: pyfftw_doc_env
+
+channels:
+  - conda-forge
+
+dependencies:
+  - cython
+  - fftw
+  - numpy
+  - python
+  - scipy
+  - sphinx

readthedocs.yml

@@ -0,0 +1,4 @@
+conda:
+  file: environment_doc.yml
+python:
+  pip_install: true

setup.py

@@ -81,6 +81,18 @@
 
 VERSION = '%d.%d.%d' % (MAJOR, MINOR, MICRO)
 
+
+if os.environ.get("READTHEDOCS") == "True":
+    try:
+        environ = os.environb
+    except AttributeError:
+        environ = os.environ
+
+    environ[b"CC"] = b"x86_64-linux-gnu-gcc"
+    environ[b"LD"] = b"x86_64-linux-gnu-ld"
+    environ[b"AR"] = b"x86_64-linux-gnu-ar"
+
+
 def get_package_data():
     from pkg_resources import get_build_platform