[cmake] set manpage name in generator function

cmake/InstallFreeRDPMan.cmake

@@ -17,6 +17,7 @@ function(generate_and_install_freerdp_man_from_template name_base section api)
     else()
       set(manpage "${CMAKE_CURRENT_BINARY_DIR}/${name_base}.${section}")
     endif()
+    set(MANPAGE_NAME ${name_base})
     cleaning_configure_file(${name_base}.${section}.in ${manpage})
     install_freerdp_man(${manpage} ${section})
   endif()