bug#49515: [core-updates] mescc-tools tests fail

["Ludovic Courtès" <ludo@gnu.org>]

On commit 9b4c3c675c05870e5983c21ce4ff944e0b0bc2fa of ‘core-updates’,
mescc-tools fails tests, with generated binaries segfaulting:

--8<---------------cut here---------------start------------->8---
$ ./pre-inst-env guix build mescc-tools

[…]

+ . ./sha256.sh
++ set -ex
++ ./bin/get_machine
+ ./bin/M1 -f test/test3/defs -f test/test3/lisp.s --BigEndian --architecture knight-native -o test/test3/hold
+ '[' amd64 = amd64 ']'
+ ./test/results/test1-binary
+ ./bin/hex2 -f elf_headers/elf32.hex2 -f test/test2/hold --LittleEndian --architecture x86 --BaseAddress 0x8048000 -o test/results/test2-binary --exec_enable
test/test1/hello.sh: line 37:   125 Segmentation fault      ./test/results/test1-binary < test/test1/hex0.hex0 > test/test1/proof1
++ ./bin/get_machine
make: *** [makefile:104: test1-binary] Error 139
make: *** Waiting for unfinished jobs....
+ '[' amd64 = x86 ']'
+ exit 0
+ . ./sha256.sh
++ set -ex
++ ./bin/get_machine
+ '[' amd64 = x86 ']'
+ exit 0
+ ./bin/hex2 -f test/test3/hold --BigEndian --architecture knight-native --BaseAddress 0 -o test/results/test3-binary
+ . ./sha256.sh
++ set -ex
test/test3/hello.sh: line 23: GET_MACHINE_FLAGS: unbound variable
+ '[' '' = 'knight*' ']'
+ exit 0

Test suite failed, dumping logs.
error: in phase 'check': uncaught exception:
%exception #<&invoke-error program: "make" arguments: ("test" "-j" "4" "PREFIX=/gnu/store/xps0k41ydjl14lx7cnrgclgsi5cnkib7-mescc-tools-0.7.0" "CC=gcc") exit-status: 2 term-signal: #f stop-signal: #f> 
phase `check' failed after 0.1 seconds
command "make" "test" "-j" "4" "PREFIX=/gnu/store/xps0k41ydjl14lx7cnrgclgsi5cnkib7-mescc-tools-0.7.0" "CC=gcc" failed with status 2
builder for `/gnu/store/lir8pmc63k1bcj4ml9gsx1769aw9ndj2-mescc-tools-0.7.0.drv' failed with exit code 1
build of /gnu/store/lir8pmc63k1bcj4ml9gsx1769aw9ndj2-mescc-tools-0.7.0.drv failed
--8<---------------cut here---------------end--------------->8---

This is a dependency of the ‘bootstrap-tarballs’ package.

Ludo’.