Fix generic unsafe.Sizeof arithmetic

[cpunion]

Summary

• return a uintptr-typed SSA value for generic unsafe.Sizeof builtin lowering
• keep divide-by-zero guard panics as runtime errors so recover observes error/RuntimeError
• add test/go coverage for generic unsafe.Sizeof shift/add/div arithmetic and unxfail fixedbugs/issue60601.go

Tests

• go test ./test/goroot -run TestGoRootRunCases -count=1 -timeout=10m -args -goroot /Users/lijie/sdk/go1.26.0 -dirs fixedbugs -case '^fixedbugs/issue60601\.go$' -directive-mode runlike -xfail /tmp/llgo-empty-xfail.yaml\n- go test ./test/go -count=1\n- go run ./cmd/llgo test ./test/go -run TestGenericUnsafeSizeofArithmetic -count=1\n- go test ./ssa -count=1\n- go test ./internal/build -count=1\n- (cd runtime && go test ./internal/runtime -count=1)\n- go test ./cl -count=1 -timeout=10m\n

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!