The RPATH contains the build path resulting in different buildid:

https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/fcitx.html

The attached patch to debian/rules passes
-DCMAKE_BUILD_RPATH_USE_ORIGIN=ON via a dh_auto_configure override,
which should use a relative path for RPATH.

With this patch applied, fcitx should build reproducibly on
tests.reproducible-builds.org!

Thanks for maintaining fcitx!

live well,
  vagrant

We believe that the bug you reported is fixed in the latest version of
fcitx, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1001868@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Boyuan Yang <byang@debian.org> (supplier of updated fcitx package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Sat, 28 May 2022 13:09:07 -0400
Source: fcitx
Architecture: source
Version: 1:4.2.9.8-8
Distribution: unstable
Urgency: medium
Maintainer: Debian Input Method Team <debian-input-method@lists.debian.org>
Changed-By: Boyuan Yang <byang@debian.org>
Closes: 1001868
Changes:
 fcitx (1:4.2.9.8-8) unstable; urgency=medium
 .
   * Team upload.
   * debian/rules: Pass -DCMAKE_BUILD_RPATH_USE_ORIGIN=ON via
   dh_auto_configure override for reproducibility. (Closes: #1001868)
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