After investigating the hasAltPkg mechanism, determined that it's not
suitable for go/build.defaultContext() because:
1. hasAltPkg works well for providing additional/alternative functions
2. But defaultContext() needs to REPLACE an existing function that depends
on internal/buildcfg, internal/goversion, and internal/platform
3. These internal packages cannot be imported from runtime/internal/lib
The full overlay approach (2073 lines) works correctly. Seeking guidance
on whether this is acceptable or if there's an alternative approach.
Demo verified working:
- runtime.Compiler = "llgo"
- go/build.Import() works correctly
- No "unknown compiler" error
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Co-authored-by: luoliwoshang <luoliwoshang@users.noreply.github.com>