Manual pages should go under ${PREFIX}/man/ rather than under
${PREFIX}/share/man/.

Index: man/CMakeLists.txt
--- man/CMakeLists.txt.orig
+++ man/CMakeLists.txt
@@ -15,7 +15,7 @@ function(one_page pname section srcname)
         )
     install(
         FILES ${CMAKE_CURRENT_BINARY_DIR}/${pname}.${section}
-        DESTINATION "${CMAKE_INSTALL_PREFIX}/share/man/man${section}"
+        DESTINATION "${CMAKE_INSTALL_PREFIX}/man/man${section}"
         )
     install(
         FILES ${CMAKE_CURRENT_BINARY_DIR}/${pname}.html