[libc][docgen] regen docgen via cmake

Author: nickdesaulniers

libc/docs/CMakeLists.txt

@@ -4,6 +4,15 @@ include(AddSphinxTarget)
 if (SPHINX_FOUND)
   if (${SPHINX_OUTPUT_HTML})
     add_sphinx_target(html libc)
+
+    list(APPEND docgen_list string strings)
+
+    foreach(stem IN LISTS docgen_list)
+      add_custom_target(${stem}_rst
+        COMMAND ${CMAKE_CURRENT_SOURCE_DIR}/../utils/docgen/docgen.py ${stem}.h >
+                ${CMAKE_CURRENT_SOURCE_DIR}/headers/${stem}.rst)
+      add_dependencies(docs-libc-html ${stem}_rst)
+    endforeach()
   endif()
 endif()
 endif()