With the default options set, ruby is also sometime failing with:

• loadpath.o ---

loadpath.c:30:2: error: RUBY_EXEC_PREFIX must be defined
^
loadpath.c:41:50: error: use of undeclared identifier 'RUBY_LIB_VERSION'
typedef char ruby_lib_version_string[(int)sizeof(RUBY_LIB_VERSION) - 2];

Sponsored by: Absolight