This commit includes following fixes for a few shell scripts:
1. Follow the best practice of quoting variables everywhere unless they
are used in places where word-splitting and globbing can never happen.
2. Replace `command` with $(command) because the latter is easier to use
and read.
3. Don't use "$@" in places expecting a string because it is an array
of strings instead of a single string.
Bash is not always installed in /bin and we should not hardcode the path
of it in source code which is expected to be built on many operating
systems and distributions.
Since most scripts using #!/bin/bash here doesn't have any bashism,
they can be converted to #!/bin/sh instead of using /usr/bin/env trick.
There are different unit-tests file generated containing lists of tests
the test-runner.sh should run. Running run-tests.sh read the unit-tests
in the current directory, which is inconvenient to do when using meson.
