Documentation: Create build folder in case it does not exist. However, add it to the git repo by placing a .gitignore inside

doc/.gitignore

@@ -1 +0,0 @@
-build/*

doc/source/conf.py

@@ -28,6 +28,10 @@ release = re.sub('^v', '', os.popen('git describe --always --tags --dirty').read
 # The short X.Y version.
 version = release
 
+try:
+	os.mkdir('../build/_doxygen')
+except FileExistsError:
+	pass
 subprocess.call('doxygen Doxyfile.in', shell=True)
 
 # -- General configuration ---------------------------------------------------