bug#29776: [core-updates] gawk fails test suite on armhf

[Mark H Weaver <mhw@netris.org>]

On core-updates, 'gawk' fails to build on armhf:

  https://hydra.gnu.org/build/2392045

Here's the tail of the build log:

--8<---------------cut here---------------start------------->8---
make[2]: Entering directory '/tmp/guix-build-gawk-4.1.4.drv-0/gawk-4.1.4/test'
1 TESTS FAILED
make[2]: *** [Makefile:4128: pass-fail] Error 1
make[2]: Leaving directory '/tmp/guix-build-gawk-4.1.4.drv-0/gawk-4.1.4/test'
make[2]: Entering directory '/tmp/guix-build-gawk-4.1.4.drv-0/gawk-4.1.4/test'
for i in _* ; \
do  \
	if [ "$i" != "_*" ]; then \
	echo ============== $i ============= ; \
	base=`echo $i | sed 's/^_//'` ; \
	if [ -r ${base}.ok ]; then \
	diff -c ${base}.ok $i ; \
	else \
	diff -c "."/${base}.ok  $i ; \
	fi ; \
	fi ; \
done 
============== _pty1 =============
*** pty1.ok	2014-01-20 19:53:01.000000000 +0000
--- _pty1	2017-12-19 09:34:25.516824947 +0000
***************
*** 1,2 ****
! 123
! x is abc
--- 1,4 ----
! sh: /dev/tty: No such device or address
! sh: /dev/tty: No such device or address
! x is 
! x is 
make[2]: *** [Makefile:4137: diffout] Error 1
make[2]: Leaving directory '/tmp/guix-build-gawk-4.1.4.drv-0/gawk-4.1.4/test'
make[1]: *** [Makefile:1651: check] Error 1
make[1]: Leaving directory '/tmp/guix-build-gawk-4.1.4.drv-0/gawk-4.1.4/test'
make: *** [Makefile:742: check-recursive] Error 1
phase `check' failed after 49.9 seconds
builder for `/gnu/store/9f8adlrb6y8f1q0zfzk49x05ly4r6lp4-gawk-4.1.4.drv' failed with exit code 1
@ build-failed /gnu/store/9f8adlrb6y8f1q0zfzk49x05ly4r6lp4-gawk-4.1.4.drv - 1 builder for `/gnu/store/9f8adlrb6y8f1q0zfzk49x05ly4r6lp4-gawk-4.1.4.drv' failed with exit code 1
--8<---------------cut here---------------end--------------->8---

        Mark