go build -overlay to patch stdlib & runtime

[ignoramous]

go.build -overlay is unsupported by gomobile. If it did, it could be used to patch runtime and stdlib at build time using flixge/go-patch-overlay as mentioned in this blog post via golang/go#69629.

Patches:

• WireGuard's monotonic time

• Changes to go/runtime/write_android_err.go instead of link time shenanigans in intra/core/overreach.go for runtime: android backtraces do not include go backtrace golang/go#25035

[ignoramous]

Local changes can be done away with. Upstream now supports -overlay:

• cmd/gomobile: -overlay build flag support golang/mobile#116

firestack/go.mod

Line 52 in c1ac730

replace golang.org/x/mobile v0.0.0-20250506005352-78cd7a343bde => github.com/ignoramous/mobile v0.0.0-20260119111959-bc2c8adf6210