build: Fix unnecessary shell quotes

Quotes aren't needed when the arguments aren't expanded by the shell.

Now paths with spaces and other nontrivial characters work.
9 jobs for fix_biuld in 20 minutes and 55 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #346768
librem5
build_deb

00:08:59

passed #346769
librem5
build_deb:amber

00:09:10

passed #346771
librem5:arm64
build_deb:arm64

00:19:08

passed #346772
librem5:arm64
build_deb:arm64_buster

00:19:19

passed #346770
librem5
build_deb:buster

00:05:55

passed #346766
librem5
build_docs

00:01:01

passed #346767
librem5
build_meson

00:08:39

 
  Test
passed #346774
librem5
test

00:03:21

passed #346773
librem5
test_lintian

00:01:35