Rewrite depfile from sbox to stay reproducible

sbox will generate a random directory for the output root, and most
tools will encode that directory name in the output target of the
depfile.

So embed the library from dep_fixer into sbox so that it can rewrite the
output filename to a static (reproducible) value. Ninja doesn't care
what that value is, so it's just "outputfile".

Also fix up rule_builder to actually tell sbox about the depfile.

Test: mmma system/iorap; check the contents of:
out/soong/.intermediates/system/iorap/libiorap-binder/android_arm_armv7-a-neon_core_static/gen/aidl/system/iorap/binder/com/google/android/startop/iorap/IIorap.cpp.d

Change-Id: I3640a2e8b0c034f143a35e398a8418a6d621b265

cmd/sbox/sbox.go

@@ -15,6 +15,7 @@
 package main
 
 import (
+	"bytes"
 	"errors"
 	"flag"
 	"fmt"
@@ -25,6 +26,8 @@ import (
 	"path/filepath"
 	"strings"
 	"time"
+
+	"android/soong/makedeps"
 )
 
 var (
@@ -152,9 +155,6 @@ func run() error {
 			return err
 		}
 		allOutputs = append(allOutputs, sandboxedDepfile)
-		if !strings.Contains(rawCommand, "__SBOX_DEPFILE__") {
-			return fmt.Errorf("the --depfile-out argument only makes sense if the command contains the text __SBOX_DEPFILE__")
-		}
 		rawCommand = strings.Replace(rawCommand, "__SBOX_DEPFILE__", filepath.Join(tempDir, sandboxedDepfile), -1)
 
 	}
@@ -281,6 +281,26 @@ func run() error {
 		}
 	}
 
+	// Rewrite the depfile so that it doesn't include the (randomized) sandbox directory
+	if depfileOut != "" {
+		in, err := ioutil.ReadFile(depfileOut)
+		if err != nil {
+			return err
+		}
+
+		deps, err := makedeps.Parse(depfileOut, bytes.NewBuffer(in))
+		if err != nil {
+			return err
+		}
+
+		deps.Output = "outputfile"
+
+		err = ioutil.WriteFile(depfileOut, deps.Print(), 0666)
+		if err != nil {
+			return err
+		}
+	}
+
 	// TODO(jeffrygaston) if a process creates more output files than it declares, should there be a warning?
 	return nil
 }