feat(overlays): add spec-set-macros overlay

[reubeno]

Summary

Adds a new declarative overlay type, spec-set-macros, for setting %global / %define macro values in RPM spec files. This replaces ~25 fragile spec-search-replace regex toggles across azurelinux — gcc.comp.toml alone has 8 such macro flips today.

Before

[[components.gcc.overlays]]
description = "Disable Ada frontend; not supported on AZL toolchain"
type = "spec-search-replace"
regex = '^%global build_ada 1$'
replacement = '%global build_ada 0'

# … 7 more nearly-identical blocks in the same file …

After

[[components.gcc.overlays]]
description = "Disable language frontends and offload targets not supported on AZL toolchain"
type = "spec-set-macros"
macros = {
    build_ada           = { value = "0" },
    build_objc          = { value = "0" },
    build_go            = { value = "0" },
    build_d             = { value = "0" },
    build_m2            = { value = "0" },
    build_cobol         = { value = "0" },
    build_offload_nvptx = { value = "0" },
    build_offload_amdgcn = { value = "0" },
}

Behavior

• The overlay accepts a map of macro names → settings; each entry has a required value and an optional kind (global or define) that forces a specific directive form.
• The directive form is auto-detected from the existing spec — users don't need to know whether upstream uses %global or %define.
• Fails if any named macro is not present in the spec — catches typos and upstream removals (a key advantage over silent regex no-ops).
• Multiple occurrences of the same macro are all updated; per-macro iteration order is sorted for deterministic rendering.
• Indentation of the original line is preserved (e.g., a %global inside an %if block stays indented). Inter-token whitespace is normalized to single spaces.

Implementation notes / divergences from the design doc

The design doc lives at the repository's TODO/01-spec-set-macros.md (not part of this PR). A few intentional divergences:

1. No inline-comment preservation. RPM does not treat # mid-line on %global / %define lines as a comment — the # and everything after it is part of the macro value. "Preserving" a trailing # comment as the design doc suggested would silently truncate legitimate values. We just replace the value portion in full.
2. ErrNoSuchMacro in the spec package rather than wrapping ErrOverlayDidNotApply. This matches the existing ErrNoSuchTag / ErrPatternNotFound convention in internal/rpm/spec/edit.go.
3. Stricter post-name match guard (\s|$) instead of \b. A request for build_ada would otherwise match %define build_ada() (function-like macro) or %global build_adapter (shared prefix). The custom guard avoids this.
4. Multi-line definitions rejected rather than rewritten. Lines ending in \ continuation get a clear ErrUnsupportedMacroDefinition error; a single-line rewrite would orphan continuation lines.
5. Macro-name validation at config load: reject empty, whitespace, %, or parentheses. Multi-line values are also rejected at load time.
6. No section / sub-package scoping in v1. Macros are typically top-level in real specs; can be added later if needed.

Testing

• 14 new SetMacro unit tests (internal/rpm/spec/edit_test.go) covering shared-prefix non-match, function-like non-match, multi-line rejection, kind override, multiple occurrences, whitespace tolerance, value-with-spaces, indentation preservation.
• 10 new validation cases (internal/projectconfig/overlay_test.go) for the new schema.
• 5 new integration cases (internal/app/azldev/core/sources/overlays_test.go) exercising the full overlay-application path including the multi-macro gcc-style case.
• mage fix all, mage check all, mage unit, mage build all pass locally.
• Schema (schemas/azldev.schema.json) regenerated.

Migration

Out of scope for this PR; a follow-up PR in azurelinux will migrate the affected *.comp.toml files (gcc, qemu, firefox, libsoup3, grub2, nbdkit, systemd, the python-* docs toggles, etc.).

Coordination

Independent of TODO 02 (spec-insert-lines-after/before + match cardinality) and TODO 03 (spec-deps). No ordering required between them.

[Copilot]

Pull request overview

Adds a new spec-set-macros overlay to declaratively update RPM %global / %define macro definitions in spec files, reducing reliance on fragile regex-based spec-search-replace overlays.

Changes:

• Introduces spec-set-macros overlay type with config/schema support (macros map with optional kind).
• Implements Spec.SetMacro() in the RPM spec editor and wires it into overlay application with deterministic macro application order.
• Updates user-facing config docs and regenerates the JSON schema.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
schemas/azldev.schema.json	Adds schema support for spec-set-macros and MacroSetSpec.
internal/rpm/spec/edit.go	Adds SetMacro editing primitive + new macro-related errors.
internal/rpm/spec/edit_test.go	Adds unit tests for SetMacro.
internal/projectconfig/overlay.go	Adds overlay config fields/types + validation for macro setting entries.
internal/projectconfig/overlay_test.go	Adds validation tests + marks new overlay as spec-modifying.
internal/app/azldev/core/sources/overlays.go	Applies spec-set-macros overlays in stable sorted order.
internal/app/azldev/core/sources/overlays_test.go	Adds integration tests for applying macro overlays end-to-end.
docs/user/reference/config/overlays.md	Documents the new overlay type and configuration.