[patch] Fix build when source directory includes @ character

[Richard Sandiford]

FX via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> Hi,
>
> Attached is a fix for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57076
> Currently, we cannot build GCC when the source directory contains a @ character (which is a problem for Homebrew, where we typically build in directories such as /tmp/gcc@10/src: https://github.com/Homebrew/brew/pull/9007)
> The problem is because gcc-vers.texi then contain an unquoted @ character, which is interpreted as a texinfo command.
> The patch fixes the rule in gcc/Makefile.in so that stray @ characters are quoted as @@
>
> Tested and bootstrapped on x86_64-apple-darwin19
>
> PS: It’s possible the same issue occurs with characters { and } in the path (according to https://www.gnu.org/software/texinfo/manual/texinfo/html_node/Conventions.html). Do you think they should be quoted too?

Yeah, seems like a good idea to fix those too.  (I checked locally
that the build does fail for a build directory called “{foo}”.)

Patch looks good otherwise though.

Thanks,
Richard