internal/pkg: optionally register binfmt

This transparently supports curing foreign exec artifacts.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/all.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"runtime"
 	"strconv"
 	"sync"
 
@@ -347,6 +348,9 @@ var (
 	// artifactsOnce is for lazy initialisation of artifacts.
 	artifactsOnce [_toolchainEnd][len(artifactsM)]sync.Once
 
+	// arch is the target architecture.
+	arch = runtime.GOARCH
+
 	// presetOpts globally modifies behaviour of presets.
 	presetOpts int
 )
@@ -358,6 +362,9 @@ const (
 	OptLLVMNoLTO
 )
 
+// Arch returns the target architecture.
+func Arch() string { return arch }
+
 // Flags returns the current preset flags
 func Flags() int { return presetOpts }
 
@@ -367,7 +374,12 @@ func zero[T any](p *T) { var v T; *p = v }
 // DropCaches arranges for all cached [pkg.Artifact] to be freed some time after
 // it returns. Must not be used concurrently with any other function from this
 // package.
-func DropCaches(flags int) {
+func DropCaches(targetArch string, flags int) {
+	if targetArch == "" {
+		targetArch = runtime.GOARCH
+	}
+
+	arch = targetArch
 	presetOpts = flags
 	zero(&artifacts)
 	zero(&artifactsOnce)