tools: tests: fix shellcheck warnings

Following up on recent discussions, this series fixes all the warnings detected by shellcheck. The resulting tools test script is now clean, at least from the perspective of shellcheck.

These fixes do not correct any known issue, other than shellcheck reporting them as potential problems, the intent is to remove common shell issues that may impact future changes, and to simplify checking that any subsequent changes to the test script constitute "good" shell.

All the patches other than Patch 8 address a particular warning. They are reasonably self-explanatory, but each commit comment includes a link to the relevant warning(s) which describes the issue and the appropriate corrections.

Patch 8 addresses a number of warnings, all related to word splitting and globbing, and those constitute the bulk of the changes. Some of the earlier patches also address trivial splitting/globbing issues where that would prevent a line being modified multiple times.

Cheers,
Kent.

Changes v1 -> v2:
- fix links in checkin comments
- fix subject of patch 2

Kent Gibson (8):
tools: tests: don't mix string and array
tools: tests: declare and assign separately
tools: tests: fix unused variables
tools: tests: use read -r to avoid mangling backslashes
tools: tests: don't use variables in printf format string
tools: tests: check exit code directly
tools: tests: shellcheck don't follow sourced file
tools: tests: avoid splitting and globbing

 tools/gpio-tools-test.bash | 459 +++++++++++++++++++------------------
 1 file changed, 234 insertions(+), 225 deletions(-)

2.39.2