Use native platform to fetch sources, generate buildroot, etc

When building for a non-native platform (typically under qemu), use the
native platform for most operations that do not need platform specific
things, such as applying patches, tarring up sources, and fetching
go module deps.

Signed-off-by: Brian Goff <[email protected]>

Author: cpuguy83

frontend/azlinux/handle_container.go

@@ -25,7 +25,7 @@ func handleContainer(w worker) gwclient.BuildFunc {
 
 			pg := dalec.ProgressGroup("Building " + targetKey + " container: " + spec.Name)
 
-			rpmDir, err := specToRpmLLB(ctx, w, client, spec, sOpt, targetKey, pg, dalec.WithPlatform(platform))
+			rpmDir, err := specToRpmLLB(ctx, w, client, spec, sOpt, targetKey, platform, pg)
 			if err != nil {
 				return nil, nil, fmt.Errorf("error creating rpm: %w", err)
 			}

frontend/azlinux/handle_depsonly.go

@@ -31,7 +31,7 @@ func handleDepsOnly(w worker) gwclient.BuildFunc {
 			if err != nil {
 				return nil, nil, err
 			}
-			st, err := specToContainerLLB(w, client, spec, targetKey, rpmDir, files, sOpt, pg)
+			st, err := specToContainerLLB(w, client, spec, targetKey, rpmDir, files, sOpt, pg, dalec.WithPlatform(platform))
 			if err != nil {
 				return nil, nil, err
 			}

frontend/azlinux/handle_rpm.go

@@ -26,7 +26,7 @@ func handleRPM(w worker) gwclient.BuildFunc {
 				return nil, nil, err
 			}
 
-			st, err := specToRpmLLB(ctx, w, client, spec, sOpt, targetKey, pg, dalec.WithPlatform(platform))
+			st, err := specToRpmLLB(ctx, w, client, spec, sOpt, targetKey, platform, pg)
 			if err != nil {
 				return nil, nil, err
 			}
@@ -64,13 +64,18 @@ func installBuildDeps(w worker, spec *dalec.Spec, targetKey string, opts ...llb.
 	}
 }
 
-func specToRpmLLB(ctx context.Context, w worker, client gwclient.Client, spec *dalec.Spec, sOpt dalec.SourceOpts, targetKey string, opts ...llb.ConstraintsOpt) (llb.State, error) {
+func specToRpmLLB(ctx context.Context, w worker, client gwclient.Client, spec *dalec.Spec, sOpt dalec.SourceOpts, targetKey string, platform *ocispecs.Platform, opts ...llb.ConstraintsOpt) (llb.State, error) {
+	// Generate the buildroot with the native platform
 	base := w.Base(client, opts...).With(installBuildDeps(w, spec, targetKey, opts...))
 	br, err := rpm.SpecToBuildrootLLB(base, spec, sOpt, targetKey, opts...)
 	if err != nil {
 		return llb.Scratch(), err
 	}
 	specPath := filepath.Join("SPECS", spec.Name, spec.Name+".spec")
+
+	// Build the RPM with the target platform
+	opts = append(opts, dalec.WithPlatform(platform))
+	base = w.Base(client, opts...).With(installBuildDeps(w, spec, targetKey, opts...))
 	st := rpm.Build(br, base, specPath, opts...)
 
 	return frontend.MaybeSign(ctx, client, st, spec, targetKey)

frontend/rpm/handle_buildroot.go

@@ -21,6 +21,8 @@ func HandleBuildroot(wf WorkerFunc) gwclient.BuildFunc {
 				return nil, nil, err
 			}
 
+			// Note, we are not passing platform down here because everything should
+			// be able to work regardless of platform, so prefer the native platform.
 			worker, err := wf(sOpt.Resolver, spec, targetKey)
 			if err != nil {
 				return nil, nil, err

frontend/rpm/handle_sources.go

@@ -25,6 +25,8 @@ func HandleSources(wf WorkerFunc) gwclient.BuildFunc {
 				return nil, nil, err
 			}
 
+			// Note, we are not passing platform down here because everything should
+			// be able to work regardless of platform, so prefer the native platform.
 			sources, err := Dalec2SourcesLLB(worker, spec, sOpt)
 			if err != nil {
 				return nil, nil, err