From b4eef59100442c292fbc54af4e07197bd367cff0 Mon Sep 17 00:00:00 2001
From: Victor Zverovich <victor.zverovich@gmail.com>
Date: Fri, 30 Jan 2015 12:53:52 -0800
Subject: [PATCH] Only add the doc target if doxygen and sphinx-build are
 available

---
 doc/CMakeLists.txt | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/doc/CMakeLists.txt b/doc/CMakeLists.txt
index 7b531f65..0dda20fe 100644
--- a/doc/CMakeLists.txt
+++ b/doc/CMakeLists.txt
@@ -1,4 +1,11 @@
+foreach (program doxygen sphinx-build)
+  find_program(${program} ${program})
+  if (NOT ${program})
+    message(STATUS "Target 'doc' disabled (requires ${program})")
+    return ()
+  endif ()
+endforeach ()
+
 add_custom_target(doc
-  COMMAND doxygen
-  COMMAND rm -rf html
-  COMMAND sphinx-build -b html . html)
+  COMMAND ${doxygen}
+  COMMAND ${sphinx-build} -b html . html)