Improves build script performance by:
* using built-ins wherever possible (e.g. string splitting)
* eliminating redundant code
* using absolute (to $KEYMAN_ROOT) rather than relative paths to avoid realpath
* removing unnecessary `npm run` calls
BEFORE | AFTER
-------------------------------|----------------------
time ./core/build.sh --help |
real 0m2.116s | real 0m0.874s
user 0m0.578s | user 0m0.198s
sys 0m0.984s | sys 0m0.289s
-------------------------------|----------------------
time ./web/build.sh --help |
real 0m3.523s | real 0m0.757s
user 0m1.166s | user 0m0.320s
sys 0m2.273s | sys 0m0.455s
-------------------------------|----------------------
time ./web/build.sh -d |
real 1m34.750s | real 0m59.974s
user 0m9.721s | user 0m6.284s
sys 0m19.652s | sys 0m13.202s
@keymanapp-test-bot skip
* `builder_has_action` renamed to `builder_start_action`
* `builder_report` renamed to `builder_finish_action`
* `builder_has_action` created to be a silent test for the action
* Added reasonably comprehensive documentation.
Fixes up scripts (except under /linux) to use `#!/usr/bin/env bash`
instead of `#!/bin/bash` or `#!/bin/sh` so that we don't end up with
the ancient version of bash supplied with macOS.
This became urgent with this PR, because of bash-4.xisms in
build-utils.sh, for example on line 572:
```
if [[ -v _builder_params[$e] ]]; then
```
Relates to #5816.
Moves folders under common/core/web to common/web:
* input-processor -> common/web/input-processor
* keyboard-processor -> common/web/keyboard-processor
* tools/recorder -> common/web/recorder
* tools/sentry-manager -> common/web/sentry-manager
* utils -> common/web/utils
Updates scripts and configuration to point to new folders.
