From <https://lists.gnu.org/archive/html/automake-patches/2015-07/msg00000.html>.
See also <http://bugs.gnu.org/22372>.

From 34163794a58b5bd91c5d6bd9adf5437571c7a479 Mon Sep 17 00:00:00 2001
From: Pavel Raiskup <praiskup@redhat.com>
Date: Tue, 7 Jul 2015 10:54:24 +0200
Subject: [PATCH] bin/automake: escape '{' in regexp pattern

Based on perlre(1) documentation:
.. in Perl v5.26, literal uses of a curly bracket will be required
to be escaped, say by preceding them with a backslash ("\{" ) or
enclosing them within square brackets ("[{]") ..

References:
https://bugzilla.redhat.com/1239379

* bin/automake.in (substitute_ac_subst_variables): Escape the
occurrence of '{' character.
---
 bin/automake.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/bin/automake.in b/bin/automake.in
index 0c29184..c294ced 100644
--- a/bin/automake.in
+++ b/bin/automake.in
@@ -3898,7 +3898,7 @@ sub substitute_ac_subst_variables_worker
 sub substitute_ac_subst_variables
 {
   my ($text) = @_;
-  $text =~ s/\${([^ \t=:+{}]+)}/substitute_ac_subst_variables_worker ($1)/ge;
+  $text =~ s/\$\{([^ \t=:+{}]+)}/substitute_ac_subst_variables_worker ($1)/ge;
   return $text;
 }
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<div class='path'>path: <a href='/guix/log/?id=1cf97f46065a5e57a03880e1983dbae28365d1de'>root</a>/<a href='/guix/log/tests?id=1cf97f46065a5e57a03880e1983dbae28365d1de'>tests</a>/<a href='/guix/log/tests/guix-system.sh?id=1cf97f46065a5e57a03880e1983dbae28365d1de'>guix-system.sh</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/guix-system.sh?id=1cf97f46065a5e57a03880e1983dbae28365d1de&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-04-21 16:16:38 +0200'>2023-04-21</span></td><td><a href='/guix/commit/tests/guix-system.sh?id=37dd69b44511dc73eb04bdebe8d82c9a0386338e'>tests: Fix checks for expected failures.</a><span class='msg-avail'>...<span class='msg-tooltip'>Addresses &lt;https://issues.guix.gnu.org/62406&gt;.

With 'set -e', a return status inverted with '!' does not cause the shell to
exit immediately.  Instead use '&amp;&amp; false' to indicate an expected failure.

* tests/guix-archive.sh, tests/guix-build-branch.sh, tests/guix-build.sh,
tests/guix-daemon.sh, tests/guix-download.sh,
tests/guix-environment-container.sh, tests/guix-environment.sh,
tests/guix-gc.sh, tests/guix-git-authenticate.sh, tests/guix-graph.sh,
tests/guix-hash.sh, tests/guix-home.sh, tests/guix-pack-relocatable.sh,
tests/guix-pack.sh, tests/guix-package-aliases.sh, tests/guix-package-net.sh,
tests/guix-package.sh, tests/guix-refresh.sh, tests/guix-shell.sh,
tests/guix-style.sh, tests/guix-system.sh: Replace uses of '! ...' with
'... &amp;&amp; false' or `test ! ...` as appropriate.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Eric Bavier</td></tr>
<tr><td><span title='2023-04-18 11:43:14 -0400'>2023-04-18</span></td><td><a href='/guix/commit/tests/guix-system.sh?id=286cdf0bc55a29d5a63f7191edde7ea4dbd8cf2a'>tests: guix-system: Drop the i686-linux desktop image test.</a><span class='msg-avail'>...<span class='msg-tooltip'>Desktop these days means having Rust support (GNOME), which i686 currently
lacks on Guix.

* tests/guix-system.sh: Do not attempt to build the desktop.tmpl image for
i686-linux.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-12-04 00:50:28 -0500'>2022-12-04</span></td><td><a href='/guix/commit/tests/guix-system.sh?id=93309efdce72ac5028944d5c1f7b081a7f62b84a'>tests: Fix guix-system.sh test.</a><span class='msg-avail'>...<span class='msg-tooltip'>The regression was introduce with commit
c7793b82efd3383a9f7adf0dfa82d71ee032e41b ("gnu: raspberry-pi: Add a
bootloader-chain for the Raspberry Pi and os examples.") due to the examples
needing to be built for the aarch64-linux system.

* tests/guix-system.sh: Invoke guix system build with '--system=aarch64-linux'
to build the Raspberry Pi systems.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-10-07 16:01:39 +0200'>2022-10-07</span></td><td><a href='/guix/commit/tests/guix-system.sh?id=31708431c53524f05e6a0c9fed920cb773e7dd21'>tests: Attempt to build 'desktop.tmpl' on all major architectures.</a><span class='msg-avail'>...<span class='msg-tooltip'>Partly fixes &lt;https://issues.guix.gnu.org/58352&gt;.

* tests/guix-system.sh: Try to build 'desktop.tmpl' for x86_64, i686, and aarch64.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-09-04 23:10:10 +0200'>2022-09-04</span></td><td><a href='/guix/commit/tests/guix-system.sh?id=f1bbb06dad36c6262afac908c45038e5a3da7b16'>guix system: Do not use 'vm-image.tmpl' in tests.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a followup to 95a03aa5c507d48e2cde19ea007b8f90a4e0108a.  Since
that commit, merely evaluating 'vm-image.tmpl' would trigger the build
of 'current-guix' so skip it.

* tests/guix-system.sh: Do not try to build 'vm-image.tmpl'.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-02-18 14:14:38 +0100'>2022-02-18</span></td><td><a href='/guix/commit/tests/guix-system.sh?id=5a57313918a5c1bd5cf8238c2dcae64a03523952'>profiles: 'profile-derivation' rejects unsupported packages.</a><span class='msg-avail'>...<span class='msg-tooltip'>Previously user-facing commands would happily start building packages
even if they do not support that system.  With this change, all the
user-facing commands reject unsupported packages without going further.

* guix/profiles.scm (profile-derivation): Add #:allow-unsupported-packages?.
Define 'check-supported-packages' and honor #:allow-unsupported-packages?.
* tests/guix-pack.sh, tests/guix-package.sh, tests/guix-shell.sh: Ensure
that unsupported packages are rejected.
* tests/guix-system.sh: Pass "--system=armhf-linux" when attempting to
build gnu/system/examples/asus-c201.tmpl.
</span></span></td><td>Ludovic Courtès</td></tr>