Generate RBE socket address randomly for each invocation of soong.

Test: started soong multiple times and saw different socket files in
out/soong/.temp

Change-Id: Ib0087dd3867bdbf584c6868196070840cff291aa

ui/build/config.go

@@ -184,7 +184,8 @@ func NewConfig(ctx Context, args ...string) Config {
 	// Tell python not to spam the source tree with .pyc files.
 	ret.environ.Set("PYTHONDONTWRITEBYTECODE", "1")
 
-	ret.environ.Set("TMPDIR", absPath(ctx, ret.TempDir()))
+	tmpDir := absPath(ctx, ret.TempDir())
+	ret.environ.Set("TMPDIR", tmpDir)
 
 	// Always set ASAN_SYMBOLIZER_PATH so that ASAN-based tools can symbolize any crashes
 	symbolizerPath := filepath.Join("prebuilts/clang/host", ret.HostPrebuiltTag(),
@@ -258,6 +259,12 @@ func NewConfig(ctx Context, args ...string) Config {
 
 	ret.environ.Set("BUILD_DATETIME_FILE", buildDateTimeFile)
 
+	if ret.UseRBE() {
+		for k, v := range getRBEVars(ctx, tmpDir) {
+			ret.environ.Set(k, v)
+		}
+	}
+
 	return Config{ret}
 }
 

ui/build/rbe.go

@@ -15,8 +15,11 @@
 package build
 
 import (
+	"fmt"
+	"math/rand"
 	"os"
 	"path/filepath"
+	"time"
 
 	"android/soong/ui/metrics"
 )
@@ -49,6 +52,11 @@ func rbeCommand(ctx Context, config Config, rbeCmd string) string {
 	return cmdPath
 }
 
+func getRBEVars(ctx Context, tmpDir string) map[string]string {
+	rand.Seed(time.Now().UnixNano())
+	return map[string]string{"RBE_server_address": fmt.Sprintf("unix://%v/reproxy_%v.sock", tmpDir, rand.Intn(1000))}
+}
+
 func startRBE(ctx Context, config Config) {
 	ctx.BeginTrace(metrics.RunSetupTool, "rbe_bootstrap")
 	defer ctx.EndTrace()