bug#40153: The guix package fails to build attempting to install something directly under /etc

[Maxim Cournoyer]

Repro:

./pre-inst-env guix build -e '((@@ (gnu packages package-management) 
current-guix))'

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 /gnu/store/9kzrrccpzl6i1sfwb0drb00gi2gwk0x0-coreutils-8.31/bin/mkdir -p 
'/gnu/store/n0w0xfnwf7j5h7138x2682rf247syp05-guix-1.0.1-15.0984481+/lib/systemd/system'
 /gnu/store/9kzrrccpzl6i1sfwb0drb00gi2gwk0x0-coreutils-8.31/bin/install -c -m 
644 etc/guix-daemon.service etc/guix-publish.service 
'/gnu/store/n0w0xfnwf7j5h7138x2682rf247syp05-guix-1.0.1-15.0984481+/lib/systemd/system'
 /gnu/store/9kzrrccpzl6i1sfwb0drb00gi2gwk0x0-coreutils-8.31/bin/mkdir -p 
'/etc/init.d'
/gnu/store/9kzrrccpzl6i1sfwb0drb00gi2gwk0x0-coreutils-8.31/bin/mkdir: cannot 
create directory ‘/etc/init.d’: Permission denied
make[3]: *** [Makefile:4851: install-nodist_sysvinitserviceDATA] Error 1
make[3]: Leaving directory '/tmp/guix-build-guix-1.0.1-15.0984481+.drv-0/source'
make[2]: *** [Makefile:5382: install-am] Error 2
make[2]: Leaving directory '/tmp/guix-build-guix-1.0.1-15.0984481+.drv-0/source'
make[1]: *** [Makefile:4899: install-recursive] Error 1
make[1]: Leaving directory '/tmp/guix-build-guix-1.0.1-15.0984481+.drv-0/source'
make: *** [Makefile:5376: install] Error 2
command "make" "install" failed with status 2
builder for 
`/gnu/store/k7ca5pbfb4vqfwggj6s9vjpcv8k0swcd-guix-1.0.1-15.0984481+.drv' failed 
with exit code 1
build of /gnu/store/k7ca5pbfb4vqfwggj6s9vjpcv8k0swcd-guix-1.0.1-15.0984481+.drv 
failed
View build log at 
'/var/log/guix/drvs/k7/ca5pbfb4vqfwggj6s9vjpcv8k0swcd-guix-1.0.1-15.0984481+.drv.bz2'.
guix build: error: build of 
`/gnu/store/k7ca5pbfb4vqfwggj6s9vjpcv8k0swcd-guix-1.0.1-15.0984481+.drv' failed
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