This package currently fails to build (at least on the amd64
architecture) with link time optimizations enabled.  For a background
for LTO please see

https://wiki.debian.org/ToolChain/LTO

The goal is to enable this optimization by default in an upcoming
Debian release in dpkg-buildflags for 64bit architectures.  The goal
is to get this package to build with link time optimizations, or to
explicitly disable link time optimizations for this package build.

To reproduce the build failure, enable the lto optimization in
testing/unstable by adding "optimize=+lto" to DEB_BUILD_MAINT_OPTIONS
in the debian/rules file, or if this macro is unset, just set it:

export DEB_BUILD_MAINT_OPTIONS = optimize=+lto

Please try to fix the build with lto enabled, fixing the packaging or
forwarding the issue upstream. If the issue cannot be fixed,
explicitly disallow building the package with lto by adding to your
rules file:

export DEB_BUILD_MAINT_OPTIONS = optimize=-lto

or adding that string to your existing setting of DEB_BUILD_MAINT_OPTIONS.

The full build log can be found at:
http://qa-logs.debian.net/2022/06/09/dpkglto/gcl_2.6.12-117_unstable_dpkglto.log
The last lines of the build log are at the end of this report.

[...]
TOP-LEVEL

SYSTEM>
NIL

SYSTEM>
"Fri Apr 22 15:51:11 UTC 2016"

SYSTEM>
*SYSTEM-BANNER*

SYSTEM>
T

SYSTEM>
INIT-CMP-ANON

SYSTEM>
#<"COMPILER" package>

COMPILER>
"sys_init.lsp"

COMPILER>
T

COMPILER>
CLTL1-COMPAT::STRING-CHAR

COMPILER>
NIL

COMPILER>
T

COMPILER>
NIL

COMPILER>
T

COMPILER>Warning: equal is not tail recursive 4096 0

NIL

COMPILER>430159360 heap words available
NIL

COMPILER>[ "t" = "" ] || \
	! [ -x /usr/bin/objdump ] || \
	! /usr/bin/objdump -f saved_pre_gcl | grep "file format" | grep "elf" || \
	! /usr/bin/objdump -R saved_pre_gcl |grep R_.*_COPY || \
	! echo "saved_pre_gcl cannot be prelinked"
saved_pre_gcl:     file format elf64-x86-64
00000000000cf900 R_X86_64_COPY     stdin@GLIBC_2.2.5
00000000000cf908 R_X86_64_COPY     rl_completion_entry_function@@Base
00000000000cf910 R_X86_64_COPY     rl_readline_name@@Base
00000000000cf920 R_X86_64_COPY     stderr@GLIBC_2.2.5
00000000000cf928 R_X86_64_COPY     stdout@GLIBC_2.2.5
saved_pre_gcl cannot be prelinked
make[2]: *** [makefile:98: saved_pre_gcl] Error 1
rm raw_pre_gcl
make[2]: Leaving directory '/<<PKGBUILDDIR>>/unixport'
make[1]: *** [makefile:81: unixport/saved_pre_gcl] Error 2
rm h/mcompdefs.h
make[1]: Leaving directory '/<<PKGBUILDDIR>>'
make: *** [debian/rules:122: build-gprof-stamp] Error 2
dpkg-buildpackage: error: debian/rules build subprocess returned exit status 2