bug#65323: build failure on Alpine Linux

[Robert Pluim <rpluim@gmail.com>]

>>>>> On Thu, 17 Aug 2023 08:44:36 +0300, Eli Zaretskii <eliz@gnu.org> said:

    >> From: Bruno Haible <bruno@clisp.org>
    >> Cc: 65323@debbugs.gnu.org
    >> Date: Thu, 17 Aug 2023 00:59:52 +0200
    >> 
    >> Eli Zaretskii wrote:
    >> 
    >> > Are we using some feature that is not standard in Awk?
    >> 

I think busyboxʼs awk is being more strict about regexp interval
expressions than eg gawk.

    Eli> Not sure if the above is at all relevant, since the error message you
    Eli> quoted comes from the build-aux/make-info-dir script, so maybe you
    Eli> should ignore everything I wrote above, and look just at that script
    Eli> and the Awk commands it runs.  (It's a poor-man's install-info.)

The following works for both gawk 5.2.1 and busybox awk 1.37.

diff --git a/build-aux/make-info-dir b/build-aux/make-info-dir
index 3490b7a31f9..64cf2d43f16 100755
--- a/build-aux/make-info-dir
+++ b/build-aux/make-info-dir
@@ -38,7 +38,7 @@
 
 exec "${AWK-awk}" '
   function detexinfo() {
-    gsub(/@value{emacsname}/, "Emacs")
+    gsub(/@value\{emacsname\}/, "Emacs")
     gsub(/@[^{]*\{/, "")
     gsub(/}/, "")
   }