fix(taskfiles): Always default to a special JOBS variable for concurrency related variables to simplify user control; Tasks that run the concurrent tools default to nprocs.

[davidlion]

Description

Currently, concurrency variables are not handled consistently so a user cannot easily control the concurrency from the command line. The goal of this PR is to create a consistent flow for users to easily control concurrency in resource limited scenarios.

For example, most tasks use the variable JOBS, but cmake also has a task that uses CMAKE_JOBS and passes that value as a JOBS argument. If the user sets JOBS it will not be respected by the task using CMAKE_JOBS. This is further complicated as top-level projects (e.g. CLP) end up using their own ad-hoc variables to control concurrency.

With this PR, we define how the default behaviour (no explicit value set) should work for concurrency related variables.

1. Low-level tasks that actually run a tool with concurrency (e.g. boost or cmake) default to the number of logical processors.
2. Any tasks propagating concurrency related variables should always default to JOBS to respect the user's value.

If the concurrency level is explicitly set by a task it will take priority over any user overrides, but this should only be used in niche cases.

Checklist

• The PR satisfies the contribution guidelines.
• This is a breaking change and that has been indicated in the PR title, OR this isn't a
  breaking change.
• Necessary docs have been updated, OR no docs need to be updated.

Validation performed

Manually tested with the boost test and prints.

Summary by CodeRabbit

• New Features

  • Build tasks now automatically use all available CPU cores by default when no parallelism value is provided.
  • Parallel build settings can now inherit from a shared default across related workflows.

• Bug Fixes

  • Improved consistency in how build concurrency is handled, reducing cases where builds fell back to tool-specific defaults.
  • Updated related task defaults so build and install steps behave more predictably together.

[coderabbitai]

Walkthrough

This PR adds a G_NPROCS variable to misc.yaml computed via getconf _NPROCESSORS_ONLN, and updates boost.yaml and cmake.yaml to default JOBS/CMAKE_JOBS concurrency variables using G_NPROCS or inheritance from JOBS, rather than defaulting to empty values. Documentation comments were adjusted accordingly.

Changes

JOBS Concurrency Defaulting

Layer / File(s)	Summary
Add shared processor-count variable exports/taskfiles/utils/misc.yaml	Adds a top-level G_NPROCS variable computed via `getconf _NPROCESSORS_ONLN`.
Boost JOBS defaulting exports/taskfiles/utils/boost.yaml	Includes misc.yaml, updates JOBS documentation, defaults build-and-install's JOBS var to G_NPROCS when unset, and removes the empty-string default for JOBS in download-and-install so it relies on the called task's defaulting.
CMake JOBS/CMAKE_JOBS defaulting exports/taskfiles/utils/cmake.yaml	Updates build task docs and defaults its JOBS var to G_NPROCS when unset; updates install-remote-tar docs and defaults CMAKE_JOBS to inherit from JOBS when unset.

Sequence Diagram(s)

sequenceDiagram
  participant Caller
  participant DownloadAndInstall
  participant BuildAndInstall
  participant InstallRemoteTar
  participant BuildTask
  participant GNPROCS

  Caller->>DownloadAndInstall: invoke (JOBS optional)
  DownloadAndInstall->>BuildAndInstall: forward JOBS
  BuildAndInstall->>GNPROCS: default JOBS to G_NPROCS if unset
  BuildAndInstall->>BuildAndInstall: run build with resolved JOBS

  Caller->>InstallRemoteTar: invoke (CMAKE_JOBS optional)
  InstallRemoteTar->>BuildTask: default CMAKE_JOBS to JOBS if unset
  BuildTask->>GNPROCS: default JOBS to G_NPROCS if unset
  BuildTask->>BuildTask: run cmake build with resolved jobs

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Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title matches the core change: standardizing concurrency-related taskfile defaults so JOBS uses nprocs where appropriate.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

exports/taskfiles/utils/boost.yaml (1)

154-160: 🩺 Stability & Availability | 🟠 Major | ⚡ Quick win

Keep a local JOBS default here. download-and-install now passes {{.JOBS}} straight through to build-and-install; if it’s unset, Task will expand that to <no value>, which prevents the child task’s default .G_NPROCS .JOBS fallback from doing its job and can surface as an invalid -j value on the default path.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@exports/taskfiles/utils/boost.yaml` around lines 154 - 160, The boost task
variables block is missing a local JOBS default, so when download-and-install
forwards {{.JOBS}} into build-and-install it can expand to <no value> and bypass
the child task’s fallback. Update the variables section in boost.yaml near
BUILD_DIR and BUILD_AND_INSTALL_ARGS to define JOBS with a default that falls
back to .G_NPROCS when .JOBS is unset, so build-and-install can safely receive a
valid jobs value.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Outside diff comments:
In `@exports/taskfiles/utils/boost.yaml`:
- Around line 154-160: The boost task variables block is missing a local JOBS
default, so when download-and-install forwards {{.JOBS}} into build-and-install
it can expand to <no value> and bypass the child task’s fallback. Update the
variables section in boost.yaml near BUILD_DIR and BUILD_AND_INSTALL_ARGS to
define JOBS with a default that falls back to .G_NPROCS when .JOBS is unset, so
build-and-install can safely receive a valid jobs value.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 22618304-b326-4ec4-9998-487ac7d8c79e

📥 Commits

Reviewing files that changed from the base of the PR and between 7947642 and b8491ae.

📒 Files selected for processing (3)

• exports/taskfiles/utils/boost.yaml
• exports/taskfiles/utils/cmake.yaml
• exports/taskfiles/utils/misc.yaml