[patch] Fix build when source directory includes @ character

[FX]

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?

Cheers,
FX

-------------- next part --------------
A non-text attachment was scrubbed...
Name: at.diff
Type: application/octet-stream
Size: 526 bytes
Desc: not available
URL: <https://gcc.gnu.org/pipermail/gcc-patches/attachments/20201031/64e179fe/attachment.obj>