Without this patch, the following build error occurs for me on NixOS:
```
$ nix-build -A clisp --check
<snipped>
Running phase: buildPhase
build flags: SHELL=/nix/store/q8qq40xg2grfh9ry1d9x4g7lq4ra7n81-bash-5.2-p21/bin/bash
ln -s ../src/.gdbinit .gdbinit
rm -f build-aux
ln -s ../src/build-aux build-aux
mkdir -p gllib
test -f gllib/Makefile || sh config.status gllib/Makefile depfiles
cd gllib && make CFLAGS="-g -O2 -no-integrated-cpp -W -Wswitch -Wcomment -Wpointer-arith -Wreturn-type -Wmissing-declarations -Wimplicit -Wno-sign-compare -Wno-format-nonliteral -Wno-shift-negative-value -O -fwrapv -pthread -fno-strict-aliasing -DNO_ASM -DENABLE_UNICODE -DMULTITHREAD -DPOSIX_THREADS -DDYNAMIC_FFI -DDYNAMIC_MODULES -fPIC -DPIC " top_srcdir="/build/source/src"
make[1]: Entering directory '/build/source/builddir/gllib'
cd /build/source/src && /nix/store/q8qq40xg2grfh9ry1d9x4g7lq4ra7n81-bash-5.2-p21/bin/bash /build/source/src/build-aux/missing automake-1.16 --gnits gllib/Makefile
/build/source/src/build-aux/missing: line 81: automake-1.16: command not found
WARNING: 'automake-1.16' is missing on your system.
You should only need it if you modified 'Makefile.am' or
'configure.ac' or m4 files included by 'configure.ac'.
The 'automake' program is part of the GNU Automake package:
<https://www.gnu.org/software/automake>
It also requires GNU Autoconf, GNU m4 and Perl in order to run:
<https://www.gnu.org/software/autoconf>
<https://www.gnu.org/software/m4/>
<https://www.perl.org/>
make[1]: *** [Makefile:1333: ../../src/gllib/Makefile.in] Error 127
make[1]: Leaving directory '/build/source/builddir/gllib'
make: *** [Makefile:648: gllib/libgnu.a] Error 2
```
This message was also reproduced by @2xsaiko on their NAS machine.
I don't know why this error sometimes occurs and sometimes does not.
On my Ubuntu machines, this error does not occur, and instead it does this:
```
Running phase: buildPhase
build flags: SHELL=/nix/store/q8qq40xg2grfh9ry1d9x4g7lq4ra7n81-bash-5.2-p21/bin/bash
ln -s ../src/.gdbinit .gdbinit
rm -f build-aux
ln -s ../src/build-aux build-aux
mkdir -p gllib
test -f gllib/Makefile || sh config.status gllib/Makefile depfiles
cd gllib && make CFLAGS="-g -O2 -no-integrated-cpp -W -Wswitch -Wcomment -Wpointer-arith -Wreturn-type -Wmissing-declarations -Wimplicit -Wno-sign-compare -Wno-format-nonliteral -Wno-shift-negative-value -O -fwrapv -pthread -fno-strict-aliasing -DNO_ASM -DENABLE_UNICODE -DMULTITHREAD -DPOSIX_THREADS -DDYNAMIC_FFI -DDYNAMIC_MODULES -fPIC -DPIC " top_srcdir="/build/source/src"
make[1]: Entering directory '/build/source/builddir/gllib'
make[2]: Entering directory '/build/source/builddir'
make[2]: Nothing to be done for 'am--refresh'.
make[2]: Leaving directory '/build/source/builddir'
cd .. && make am--refresh
make[2]: Entering directory '/build/source/builddir'
make[2]: Nothing to be done for 'am--refresh'.
make[2]: Leaving directory '/build/source/builddir'
<snipped>
```
In any case, these changes work successfully on all platforms I've tested them on:
1. NixOS
2. Ubuntu 22.04
3. MacOS x86_64
4. MacOS aarch64
This function is not, and never have been, used anywhere inside nixpkgs, outside of bootstrapping setupcfg2nix itself.
It was added in https://github.com/NixOS/nixpkgs/pull/38778 by @shlevy.
It has no out-of-tree users on Github either. External breakage is not expected.
