-option(GMX_BUILD_HELP "Build man pages, HTML help, and completions automatically (requires that compiled binaries can be executed on the build host)" OFF)
+# Value of AUTO tries to generate things, but will only produce warnings if
+# that fails.
+set(build_help_default AUTO)
+if (SOURCE_IS_SOURCE_DISTRIBUTION)
+ set(build_help_default OFF)
+endif()
+gmx_option_trivalue(GMX_BUILD_HELP "Build man pages, HTML help, and completions automatically (requires that compiled binaries can be executed on the build host)" ${build_help_default})