Use go:build directives in generated files.

Build constraints are now inferred from go:build directives rather than +build
directives. +build directives are still emitted in generated files as required
in Go 1.16 and earlier.

Note that go/build/constraint was added in Go 1.16, so gVisor now requires Go
1.16.

PiperOrigin-RevId: 387240779

2 files changed, 8 insertions, 5 deletions

diff --git a/tools/go_stateify/BUILD b/tools/go_stateify/BUILD
index 913558b4e..ad66981c7 100644
--- a/tools/go_stateify/BUILD
+++ b/tools/go_stateify/BUILD
@@ -6,7 +6,7 @@ go_binary(
     name = "stateify",
     srcs = ["main.go"],
     visibility = ["//:sandbox"],
-    deps = ["//tools/tags"],
+    deps = ["//tools/constraintutil"],
 )
 
 bzl_library(
diff --git a/tools/go_stateify/main.go b/tools/go_stateify/main.go
index 93022f504..7216388a0 100644
--- a/tools/go_stateify/main.go
+++ b/tools/go_stateify/main.go
@@ -28,7 +28,7 @@ import (
 	"strings"
 	"sync"
 
-	"gvisor.dev/gvisor/tools/tags"
+	"gvisor.dev/gvisor/tools/constraintutil"
 )
 
 var (
@@ -214,10 +214,13 @@ func main() {
 	// Automated warning.
 	fmt.Fprint(outputFile, "// automatically generated by stateify.\n\n")
 
-	// Emit build tags.
-	if t := tags.Aggregate(flag.Args()); len(t) > 0 {
-		fmt.Fprintf(outputFile, "%s\n\n", strings.Join(t.Lines(), "\n"))
+	// Emit build constraints.
+	bcexpr, err := constraintutil.CombineFromFiles(flag.Args())
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to infer build constraints: %v", err)
+		os.Exit(1)
 	}
+	outputFile.WriteString(constraintutil.Lines(bcexpr))
 
 	// Emit the package name.
 	_, pkg := filepath.Split(*fullPkg)