fix to no libomp in rtd build

docs/conf.py

@@ -20,6 +20,7 @@ else:
     import site
     p = site.getsitepackages()[0]
     sys.path.insert(0, p)
+    os.environ[b"CC"] = b"x86_64-linux-gnu-gcc"
 
 # -- Project information -----------------------------------------------------
 

docs/rtd_environment.yml

@@ -8,6 +8,7 @@ dependencies:
   - python=3.7
   - cythongsl
   - gsl
+  - llvm-openmp
   - h5py
   - numpy
   - scipy