llvm-tools: build host llvm-objcopy/strip/profdata under ZigToolchain

[henderkes]

Add an llvm-tools target artifact that downloads llvm-project source matching the version of clang shipped by the active zig install, builds llvm-objcopy, llvm-strip and llvm-profdata into PKG_ROOT_PATH/llvm-tools/bin, and exposes them through the same path/binary/isInstalled static surface as the other artifacts.

A new LlvmToolsCheck doctor item runs when the active toolchain is ZigToolchain and reports whether the three tools are built, with a fix that installs the package and runs the build.

PackageBuilder now picks the right tool when the active toolchain is ZigToolchain:

• extractDebugInfo() honours OBJCOPY from the environment, then falls back to llvm-tools' llvm-objcopy under Zig and plain objcopy otherwise.
• stripBinary() uses llvm-strip under Zig and plain strip otherwise.

System strip/objcopy refuse zig-produced archives and bitcode sections, so without this the strip stage breaks LTO builds. Other toolchains keep using the system binaries.

ApplicationContext::tryGet() wraps the container's get() in a try/catch and returns null on failure, so PackageBuilder can ask "which toolchain is active right now" without PHP-DI throwing on autowirable-but-unconstructable classes.

Depends on v3c/artifact-static-helpers (uses zig::isInstalled() and zig::binary()).

What does this PR do?

Checklist before merging

• If you modified *.php or *.yml, run them locally to ensure your changes are valid:
  • composer cs-fix
  • composer analyse
  • composer test
  • bin/spc dev:lint-config