I found in all make warning / error messages, it uses a single back quote but then a single quote to highlight the user input.
For example, the error message of the undefined makefile name is like
Makefile `xxx' was not found.
At first I thought it was a typo, but it seems to me it is intended for all messages.
https://www.gnu.org/software/make/manual/html_node/Error-Messages.html
It is distinct from the modern development to use both single / double quote around the highlight text, e.g. Makefile 'xxx' was not found.
Does anyone know the reason behind it?
