sys: check in generated files

We used to have all generated files checked in.
Later we removed them (now users are supposed to
run make to generate them). This causes several
problems:

 - go get does not work as it tries to build everything
   straight away (go get -d works, but users are confused)
 - users don't run make and complain that build is broken
 - users don't re-run make after updates and complain that
   build is broken
 - hard to integrate into other build system (even if they
   support building Go, they don't support running sysgen
   out-of-the-box)

Fixes #216

.gitignore

@@ -4,7 +4,3 @@
 workdir*
 
 bin/
-sys/sys_amd64.go
-sys/sys_arm64.go
-sys/sys_ppc64le.go
-executor/syscalls.h

Makefile

@@ -9,7 +9,6 @@ endif
 .PHONY: all format clean manager fuzzer executor execprog mutate prog2c stress extract generate repro
 
 all:
-	$(MAKE) generate
 	go install ./syz-manager ./syz-fuzzer
 	$(MAKE) manager
 	$(MAKE) fuzzer

sysgen/sysgen.go

@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"flag"
 	"fmt"
+	"go/format"
 	"io"
 	"io/ioutil"
 	"os"
@@ -810,7 +811,12 @@ func isIdentifier(s string) bool {
 	return true
 }
 
-func writeSource(file string, src []byte) {
+func writeSource(file string, data []byte) {
+	src, err := format.Source(data)
+	if err != nil {
+		fmt.Printf("%s\n", data)
+		failf("failed to format output: %v", err)
+	}
 	if oldSrc, err := ioutil.ReadFile(file); err == nil && bytes.Equal(src, oldSrc) {
 		return
 	}