fix: 🐛 Add .gitattributes & Update .gitignore

Add .gitattributes to avoid line ending problems of perl scripts in /utils . All .pl file will be forced to end with LF. Update .gitignore to ignore clion dir.

有时git会将utils中两个perl脚本的换行符更改为crlf，造成比较令人困惑的问题：

> make

AS boot/start.S
CC boot/boot.c
LD -> build/boot/boot
CREATE -> build/boot/boot.img
make: utils/genboot.pl: No such file or directory
make: *** [Makefile:85: build/boot/boot.img] Error 127