Allow runtime cgo implicit dependency

[feicong]

No description provided.

[mvdan]

What bug is this fixing? And we need a test.

[feicong]

This patch is needed because cgo builds implicitly depend on runtime/cgo, but listPackage only treated runtime as an always-
allowed implicit dependency. When building the code with CGO_ENABLED=1, Garble fails with:

list runtime/cgo: not a dependency
exit status 1

Allowing runtime/cgo here matches the toolchain’s implicit cgo dependency behavior and fixes the failure.

[mvdan]

Thanks. Do you have a reproducer? See the bug template when you file an issue. It doesn't make any sense to merge a fix without some sort of regression test.

[mvdan]

Closing this for now.

[tomac]

Environment

• garble version: v0.16.0
• go version: go1.26.4 linux/amd64

Files

go.mod
module repro

go 1.26

main.go

package main

func main() { println("hello") }

Steps

fails

CGO_ENABLED=1 garble build -buildmode=pie
-ldflags '-linkmode external -extldflags "-static-pie"' -o /tmp/a .

succeeds — identical flags, plain toolchain (control)

CGO_ENABLED=1 go build -buildmode=pie
-ldflags '-linkmode external -extldflags "-static-pie"' -o /tmp/b .

Expected: garble builds the binary, like go build does.

Actual:

repro

list runtime/cgo: not a dependency
exit status 1

[tomac]

Thanks @mvdan ! Do you need any further information to reproduce the error? Thanks!

[mvdan]

Thanks @tomac for the pointer. I'll push a new version of this PR which adds a regression test and a more general fix.