Fix failing tests for msys2 mingw build.

[Syed-Shahrukh-OSSRevival]

Making check in tools
make[1]: Entering directory '/d/a/enca/enca/tools'
make  check-am
make[2]: Entering directory '/d/a/enca/enca/tools'
make[2]: Nothing to be done for 'check-am'.
make[2]: Leaving directory '/d/a/enca/enca/tools'
make[1]: Leaving directory '/d/a/enca/enca/tools'
Making check in script
make[1]: Entering directory '/d/a/enca/enca/script'
make[1]: Nothing to be done for 'check'.
make[1]: Leaving directory '/d/a/enca/enca/script'
Making check in lib
make[1]: Entering directory '/d/a/enca/enca/lib'
make[1]: Nothing to be done for 'check'.
make[1]: Leaving directory '/d/a/enca/enca/lib'
Making check in src
make[1]: Entering directory '/d/a/enca/enca/src'
make  check-am
make[2]: Entering directory '/d/a/enca/enca/src'
make[2]: Nothing to be done for 'check-am'.
make[2]: Leaving directory '/d/a/enca/enca/src'
make[1]: Leaving directory '/d/a/enca/enca/src'
Making check in devel-docs
make[1]: Entering directory '/d/a/enca/enca/devel-docs'
make[1]: Nothing to be done for 'check'.
make[1]: Leaving directory '/d/a/enca/enca/devel-docs'
Making check in test
make[1]: Entering directory '/d/a/enca/enca/test'
make  check-TESTS
make[2]: Entering directory '/d/a/enca/enca/test'
make[3]: Entering directory '/d/a/enca/enca/test'
PASS: test-lists.sh
FAIL: test-long-texts.sh
FAIL: test-convlist.sh
FAIL: test-guess-unknown.sh
FAIL: test-guess-short.sh
FAIL: test-guess-stdin.sh
FAIL: test-guess-utf[8](https://github.com/nijel/enca/actions/runs/15309259996/job/43069684724#step:7:9).sh
FAIL: test-pP.sh
PASS: test-aliases.sh
PASS: test-empty.sh
FAIL: test-convert-64.sh
FAIL: test-convert-filter.sh
PASS: test-errors.sh
FAIL: test-ENCAOPT.sh
FAIL: test-default-cs.sh
SKIP: test-external.sh
FAIL: test-iconv.sh
SKIP: test-tex.sh
PASS: test-locale.sh
PASS: test-simtable.sh
SKIP: test-recode.sh
============================================================================
Testsuite summary for Enca 1.20-dev
============================================================================
# TOTAL: 21
# PASS:  6
# SKIP:  3
# XFAIL: 0
# FAIL:  12
# XPASS: 0
# ERROR: 0
============================================================================
See test/test-suite.log
Please report to https://github.com/nijel/enca/issues
============================================================================
make[3]: *** [Makefile:[9](https://github.com/nijel/enca/actions/runs/15309259996/job/43069684724#step:7:10)03: test-suite.log] Error 1
make[3]: Leaving directory '/d/a/enca/enca/test'
make[2]: *** [Makefile:[10](https://github.com/nijel/enca/actions/runs/15309259996/job/43069684724#step:7:11)11: check-TESTS] Error 2
make[2]: Leaving directory '/d/a/enca/enca/test'
make[1]: *** [Makefile:[12](https://github.com/nijel/enca/actions/runs/15309259996/job/43069684724#step:7:13)26: check-am] Error 2
make[1]: Leaving directory '/d/a/enca/enca/test'
make: *** [Makefile:568: check-recursive] Error 1
Error: Process completed with exit code 2.