runtime: add line info for stack frames

[cpunion]

Adds compact LLGo runtime funcinfo metadata and uses it for stack/function lookup.

• Emits DCE-safe function metadata as strings and links a compact table/string blob/hash table into the binary.
• Resolves runtime.Caller, CallersFrames, FuncForPC, runtime.Stack, and debug.Stack through dladdr, cached StackTrace frame names, and funcinfo. Linux funcinfo executables narrowly export main-frame dynamic symbols for dladdr.
• Removes the LLGO_LINEINFO/DWARF/dSYM/llvm-symbolizer path; this PR provides function-level source positions, not statement-level line tables.
• Preserves stack API frames under optimization by marking the runtime stack wrappers noinline and disabling tail calls there.

Tests cover funcinfo encoding/table emission, DCE safety, Linux link flags, //go:noinline attributes, renamed symbols, Caller/CallersFrames/FuncForPC/Stack/debug.Stack, and fixedbugs/issue29735.go.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[cpunion]

Added c9c9cad to cover the Codecov patch gap in cl/compile.go.\n\nWhat changed:\n- Added TestDebugOnlyValueReferrerHelpers in cl/builtin_test.go.\n- It directly covers hasNoSemanticReferrers, debugOnlyPureValue, and the compileInstr debug-only pure value skip branch.\n\nLocal verification:\n- go test ./cl -run 'Test(DebugOnlyValueReferrerHelpers|CompileLargeNilDerefInterfaceGuards)$' -coverprofile=/tmp/llgo-cl-focused.cover\n - go tool cover shows hasNoSemanticReferrers: 100%, debugOnlyPureValue: 100%, and the compileInstr skip branch covered.\n- go test ./cl -run 'Test(DebugOnlyValueReferrerHelpers|CompileLargeNilDerefInterfaceGuards|CompileRangeFuncDeferModule|RangeFuncDeferAnalysisHelpers)$' -count=1\n\nCI/Codecov are pending a fresh run for the new head commit.

[cpunion]

Resolved the latest merge conflict with xgo-dev/main (51d665e). Kept this PR's broader litgen debug metadata handling and did not re-add fixedbugs/issue29735.go to xfail, since it is covered by this PR.\n\nLocal verification:\n- go test -timeout 20m ./chore/litgen -count=1\n- go test -timeout 20m ./cl -run 'Test(DebugOnlyValueReferrerHelpers|CompileLargeNilDerefInterfaceGuards|CompileRangeFuncDeferModule|RangeFuncDeferAnalysisHelpers)$' -count=1\n- git diff --check

[zhouguangyuan0718]

这里记录的原始信息是函数定义的位置的文件名 行号等信息 这样的话 运行时恢复的堆栈就也是定义的位置，而不是调用的位置，这个是预期的吗？

[cpunion]

之前是自定义定义位置加上 llvm-symbolizer，感觉太重了，这个 PR 先移掉。#2002 尝试把调用行也加进来，对比一下数据和运行时开销，先 draft

[cpunion]

Closing as superseded by #2002. The runtime funcinfo/line metadata plan is now tracked in #2004; any remaining stack/function lookup work should build on #2002 rather than this older function-level lineinfo branch.