Remove --multitree-build

Multitree has been discontinued.

Test: m nothing --no-skip-soong-tests
Change-Id: Ie4d96a11279bf0f20a5e1a49837d9df4b24b1662

ui/build/config.go

@@ -75,7 +75,6 @@ type configImpl struct {
 	queryview                bool
 	reportMkMetrics          bool // Collect and report mk2bp migration progress metrics.
 	soongDocs                bool
-	multitreeBuild           bool // This is a multitree build.
 	skipConfig               bool
 	skipKati                 bool
 	skipKatiNinja            bool
@@ -424,10 +423,6 @@ func NewConfig(ctx Context, args ...string) Config {
 	// zip files produced by soong_zip.  Disable zipbomb detection.
 	ret.environ.Set("UNZIP_DISABLE_ZIPBOMB_DETECTION", "TRUE")
 
-	if ret.MultitreeBuild() {
-		ret.environ.Set("MULTITREE_BUILD", "true")
-	}
-
 	outDir := ret.OutDir()
 	buildDateTimeFile := filepath.Join(outDir, "build_date.txt")
 	if buildDateTime, ok := ret.environ.Get("BUILD_DATETIME"); ok && buildDateTime != "" {
@@ -789,8 +784,6 @@ func (c *configImpl) parseArgs(ctx Context, args []string) {
 			c.skipMetricsUpload = true
 		} else if arg == "--mk-metrics" {
 			c.reportMkMetrics = true
-		} else if arg == "--multitree-build" {
-			c.multitreeBuild = true
 		} else if arg == "--search-api-dir" {
 			c.searchApiDir = true
 		} else if strings.HasPrefix(arg, "--ninja_weight_source=") {
@@ -1095,10 +1088,6 @@ func (c *configImpl) IsVerbose() bool {
 	return c.verbose
 }
 
-func (c *configImpl) MultitreeBuild() bool {
-	return c.multitreeBuild
-}
-
 func (c *configImpl) NinjaWeightListSource() NinjaWeightListSource {
 	return c.ninjaWeightListSource
 }