[Bug c++/121963] Make it easier to change the location of gcm.cache dir and document it

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121963

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Can you please fix your new blog post to not misattribute Nathaniel's comment
to me.