*.d format is version-independent
As pointed out by on ,
multi-path in single-line could be appear even with older-gcc or clang.
MODIFY
lib/mruby/build/command.rb
lib/mruby/build/command.rb
@@ -133,27 +133,14 @@ module MRuby
#
# ==== Without <tt>-MP</tt> compiler flag
#
- # /build/host/src/array.o: \
- # /src/array.c \
- # /include/mruby/common.h \
- # /include/mruby/value.h \
- # /src/value_array.h
- #
- # ==== Without <tt>-MP</tt> compiler flag (gcc (Ubuntu 9.3.0-10ubuntu2) 9.3.0)
- #
# /build/host/src/array.o: /src/array.c \
- # /include/mruby.h /include/mrbconf.h \
- # /include/mruby/common.h \
- # ...
- # /include/mruby/range.h \
+ # /include/mruby/common.h /include/mruby/value.h \
# /src/value_array.h
#
# ==== With <tt>-MP</tt> compiler flag
#
- # /build/host/src/array.o: \
- # /src/array.c \
- # /include/mruby/common.h \
- # /include/mruby/value.h \
+ # /build/host/src/array.o: /src/array.c \
+ # /include/mruby/common.h /include/mruby/value.h \
# /src/value_array.h
#
# /include/mruby/common.h:

*.d format is version-independent

As pointed out by @shuujii on https://github.com/mruby/mruby/pull/5079 ,
multi-path in single-line could be appear even with older-gcc or clang.