Do not skip eval of ENABLE_DOXYGEN/_MANUAL if doxgen not found
see https://bugs.gentoo.org/977904

diff --git a/docs/CMakeLists.txt b/docs/CMakeLists.txt
index e8e1859..902017c 100644
--- a/docs/CMakeLists.txt
+++ b/docs/CMakeLists.txt
@@ -108,7 +108,6 @@ endif(ENABLE_MAN_PAGES)
 find_package(Doxygen)
 if (NOT Doxygen_FOUND)
   message(STATUS "Doxygen not found - skipping API/Doxygen and Manual components.")
-  return()
 endif()
 set(ENABLE_MANUAL_OR_DOXYGEN false)