Test suite failures on childproc.t and art.t

I've been trying to build and package watchman, but the test failures I'm getting are difficult for me to decipher. Could someone suggest the root cause?

```
make check-TESTS
make[1]: Entering directory '/tmp/guix-build-watchman-4.9.0.drv-0/source'
make[2]: Entering directory '/tmp/guix-build-watchman-4.9.0.drv-0/source'
PASS: tests/cache.t
PASS: tests/bser.t
PASS: tests/future.t
./test-driver: line 107: 5772 Aborted (core dumped) "$@" > $log_file 2>&1
FAIL: tests/childproc.t
PASS: tests/result.t
PASS: tests/string.t
PASS: tests/log.t
PASS: tests/wildmatch.t
PASS: tests/pending.t
./test-driver: line 107: 5770 Segmentation fault (core dumped) "$@" > $log_file 2>&1
FAIL: tests/art.t
PASS: tests/ignore.t
============================================================================
Testsuite summary for watchman 4.9.0
============================================================================
# TOTAL: 11
# PASS: 9
# SKIP: 0
# XFAIL: 0
# FAIL: 2
# XPASS: 0
# ERROR: 0
============================================================================
See ./test-suite.log
============================================================================
make[2]: *** [Makefile:4664: test-suite.log] Error 1
make[2]: Leaving directory '/tmp/guix-build-watchman-4.9.0.drv-0/source'
make[1]: *** [Makefile:4772: check-TESTS] Error 2
make[1]: Leaving directory '/tmp/guix-build-watchman-4.9.0.drv-0/source'
make: *** [Makefile:5054: check-am] Error 2

Test suite failed, dumping logs.

--- ./test-suite.log --------------------------------------------------------

======================================
watchman 4.9.0: ./test-suite.log
======================================

# TOTAL: 11
# PASS: 9
# SKIP: 0
# XFAIL: 0
# FAIL: 2
# XPASS: 0
# ERROR: 0

.. contents:: :depth: 2

FAIL: tests/art.t
=================

1..84
ok 1 - tests/art_test.cpp:109 t.size() == 2
ok 2 - tests/art_test.cpp:146 l && l->key == "A"
ok 3 - tests/art_test.cpp:150 l && l->key == "zythum"
FAIL tests/art.t (exit status: 139)

FAIL: tests/childproc.t
=======================

1..5
2020-05-08T03:03:32,506: [] ChildProcess: pid=0
2020-05-08T03:03:32,506: [] argv[0] /bin/echo
2020-05-08T03:03:32,506: [] argv[1] hello
2020-05-08T03:03:32,506: [] envp[0] _=./tests/childproc.t
2020-05-08T03:03:32,506: [] envp[1] PATH=/gnu/store/xxv1sk5y2bzi08v13dzs8cmsnivqsf22-automake-1.16.1/bin:/gnu/store/wqg1phrny7vdc6ns7qxb0d7rq8j1bwmw-autoconf-2.69/bin:/gnu/store/222gr37iybb5cnwxcrz1i45jinp415c2-libtool-2.4.6/bin:/gnu/store/i1cqaixp79vd3qwnyj1ll10pq6skm2wk-pkg-config-0.29.2/bin:/gnu/store/k2m4q2av9hw73hw2jx6qrxqdyh855398-openssl-1.1.1c/bin:/gnu/store/l8nphg0idd8pfddyad8f92lx8d1hc053-python-wrapper-3.7.4/bin:/gnu/store/cnqpra8vr2l5fz00rr4yj4bp3hr00cfw-tar-1.32/bin:/gnu/store/py3k9zla9fj3z7430v4crqj5pyrsd3qj-gzip-1.10/bin:/gnu/store/l86azr7r3p5631wj3kk329jl1y1mpjgy-bzip2-1.0.6/bin:/gnu/store/lbip9isk25isymvnb159l115xnacb5j8-xz-5.2.4/bin:/gnu/store/6jdshxwdrad9mlhcqc9k0g24yw45rqf1-file-5.33/bin:/gnu/store/58sq8iabw3jkv0fvf95hd7sq2g4xcsnz-diffutils-3.7/bin:/gnu/store/v76scv4n63ip08g119rczh2mrw31zwpd-patch-2.7.6/bin:/gnu/store/g9d3wv1d68iflx57yp3mcp3k3sv8spsl-findutils-4.6.0/bin:/gnu/store/2z9hsww76aag37p40671l9niq5pvvasx-gawk-5.0.1/bin:/gnu/store/afmvfw1yhfal48n1kjq6bk6kcw8sc3db-sed-4.7/bin:/gnu/store/7iyvxhp2g3v3655zqwr6biz2h0lqv7pr-grep-3.3/bin:/gnu/store/9kzrrccpzl6i1sfwb0drb00gi2gwk0x0-coreutils-8.31/bin:/gnu/store/b5vpfzkr59bpgcsg1k9vvad9h5rwvpgk-make-4.2.1/bin:/gnu/store/29jhbbg1hf557x8j53f9sxd9imlmf02a-bash-minimal-5.0.7/bin:/gnu/store/nc5vlidpxbvngalng30nif8nb3j7gfy2-ld-wrapper-0/bin:/gnu/store/3hkdiscs4910r75njbrql10znxxn7chk-binutils-2.32/bin:/gnu/store/x3jx25cd3q363mr7nbgzrhrv1vza6cf7-gcc-7.4.0/bin:/gnu/store/ahqgl4h89xqj695lgqvsaf6zh2nhy4pj-glibc-2.29/bin:/gnu/store/ahqgl4h89xqj695lgqvsaf6zh2nhy4pj-glibc-2.29/sbin:/gnu/store/42myw0y4q2djyajzc9i5i4inwr2831nv-m4-1.4.18/bin:/gnu/store/78w7y0lxar70j512iqw8x3nimzj10yga-python-3.7.4/bin
2020-05-08T03:03:32,506: [] envp[2] LC_ALL=en_US.utf8
2020-05-08T03:03:32,506: [] envp[3] NIX_BUILD_TOP=/tmp/guix-build-watchman-4.9.0.drv-0
2020-05-08T03:03:32,506: [] envp[4] SHLVL=3
2020-05-08T03:03:32,506: [] envp[5] CPATH=/gnu/store/k2m4q2av9hw73hw2jx6qrxqdyh855398-openssl-1.1.1c/include:/gnu/store/l86azr7r3p5631wj3kk329jl1y1mpjgy-bzip2-1.0.6/include:/gnu/store/lbip9isk25isymvnb159l115xnacb5j8-xz-5.2.4/include:/gnu/store/6jdshxwdrad9mlhcqc9k0g24yw45rqf1-file-5.33/include:/gnu/store/2z9hsww76aag37p40671l9niq5pvvasx-gawk-5.0.1/include:/gnu/store/b5vpfzkr59bpgcsg1k9vvad9h5rwvpgk-make-4.2.1/include:/gnu/store/3hkdiscs4910r75njbrql10znxxn7chk-binutils-2.32/include:/gnu/store/x3jx25cd3q363mr7nbgzrhrv1vza6cf7-gcc-7.4.0/include:/gnu/store/ahqgl4h89xqj695lgqvsaf6zh2nhy4pj-glibc-2.29/include:/gnu/store/78w7y0lxar70j512iqw8x3nimzj10yga-python-3.7.4/include:/gnu/store/7czrqpi0kwazras6pgyx0bhdn89pg0jl-linux-libre-headers-4.19.56/include
2020-05-08T03:03:32,506: [] envp[6] LIBRARY_PATH=/gnu/store/k2m4q2av9hw73hw2jx6qrxqdyh855398-openssl-1.1.1c/lib:/gnu/store/l86azr7r3p5631wj3kk329jl1y1mpjgy-bzip2-1.0.6/lib:/gnu/store/lbip9isk25isymvnb159l115xnacb5j8-xz-5.2.4/lib:/gnu/store/6jdshxwdrad9mlhcqc9k0g24yw45rqf1-file-5.33/lib:/gnu/store/2z9hsww76aag37p40671l9niq5pvvasx-gawk-5.0.1/lib:/gnu/store/3hkdiscs4910r75njbrql10znxxn7chk-binutils-2.32/lib:/gnu/store/ahqgl4h89xqj695lgqvsaf6zh2nhy4pj-glibc-2.29/lib:/gnu/store/qky1x5bb2jygy58bn6y95ygfsmpakf52-glibc-2.29-static/lib:/gnu/store/mmqp1xqffn6qw6v88i627c2bpbq36fcy-glibc-utf8-locales-2.29/lib:/gnu/store/78w7y0lxar70j512iqw8x3nimzj10yga-python-3.7.4/lib
2020-05-08T03:03:32,506: [] envp[7] ARCHFLAGS=
2020-05-08T03:03:32,506: [] envp[8] TMP=/tmp/guix-build-watchman-4.9.0.drv-0
2020-05-08T03:03:32,506: [] envp[9] ACLOCAL_PATH=/gnu/store/xxv1sk5y2bzi08v13dzs8cmsnivqsf22-automake-1.16.1/share/aclocal:/gnu/store/222gr37iybb5cnwxcrz1i45jinp415c2-libtool-2.4.6/share/aclocal:/gnu/store/i1cqaixp79vd3qwnyj1ll10pq6skm2wk-pkg-config-0.29.2/share/aclocal
2020-05-08T03:03:32,506: [] envp[10] GUIX_LOCPATH=/gnu/store/mmqp1xqffn6qw6v88i627c2bpbq36fcy-glibc-utf8-locales-2.29/lib/locale
2020-05-08T03:03:32,506: [] envp[11] PYTHONPATH=/gnu/store/78w7y0lxar70j512iqw8x3nimzj10yga-python-3.7.4/lib/python3.7/site-packages
2020-05-08T03:03:32,506: [] envp[12] GUIX_LD_WRAPPER_ALLOW_IMPURITIES=no
2020-05-08T03:03:32,506: [] envp[13] MAKEFLAGS=w -j4 --jobserver-auth=3,4 -- TEST_LOGS=tests/art.t.log\ tests/bser.t.log\ tests/cache.t.log\ tests/childproc.t.log\ tests/future.t.log\ tests/ignore.t.log\ tests/pending.t.log\ tests/result.t.log\ tests/string.t.log\ tests/log.t.log\ tests/wildmatch.t.log
2020-05-08T03:03:32,506: [] envp[14] TEMP=/tmp/guix-build-watchman-4.9.0.drv-0
2020-05-08T03:03:32,506: [] envp[15] MFLAGS=-w -j4 --jobserver-auth=3,4
2020-05-08T03:03:32,506: [] envp[16] TMPDIR=/tmp/guix-build-watchman-4.9.0.drv-0
2020-05-08T03:03:32,506: [] envp[17] NIX_STORE=/gnu/store
2020-05-08T03:03:32,506: [] envp[18] MAKELEVEL=3
2020-05-08T03:03:32,506: [] envp[19] srcdir=.
2020-05-08T03:03:32,506: [] envp[20] HOME=/homeless-shelter
2020-05-08T03:03:32,506: [] envp[21] out=/gnu/store/9s6lln0kzh67wy03nvs3n65ji480kgk4-watchman-4.9.0
2020-05-08T03:03:32,506: [] envp[22] TEMPDIR=/tmp/guix-build-watchman-4.9.0.drv-0
2020-05-08T03:03:32,506: [] envp[23] MAKEOVERRIDES=${-*-command-variables-*-}
2020-05-08T03:03:32,506: [] envp[24] SOURCE_DATE_EPOCH=1
2020-05-08T03:03:32,506: [] envp[25] TEST_LOGS=tests/art.t.log tests/bser.t.log tests/cache.t.log tests/childproc.t.log tests/future.t.log tests/ignore.t.log tests/pending.t.log tests/result.t.log tests/string.t.log tests/log.t.log tests/wildmatch.t.log
2020-05-08T03:03:32,506: [] envp[26] PKG_CONFIG_PATH=/gnu/store/k2m4q2av9hw73hw2jx6qrxqdyh855398-openssl-1.1.1c/lib/pkgconfig:/gnu/store/lbip9isk25isymvnb159l115xnacb5j8-xz-5.2.4/lib/pkgconfig:/gnu/store/78w7y0lxar70j512iqw8x3nimzj10yga-python-3.7.4/lib/pkgconfig
2020-05-08T03:03:32,506: [] envp[27] PWD=/tmp/guix-build-watchman-4.9.0.drv-0/source
2020-05-08T03:03:32,506: [] envp[28] NIX_BUILD_CORES=0
terminate called after throwing an instance of 'std::system_error'
what(): posix_spawnp: No such file or directory
FAIL tests/childproc.t (exit status: 134)
```