Deprecate USE_GOMA and replace with FORCE_USE_GOMA

Bug: b/163361527
Test: Ran builds with USE_GOMA / FORCE_USE_GOMA flags
Change-Id: I67b229fbf52e913b0c4f5e7932021132ddc0598f
diff --git a/cmd/soong_ui/main.go b/cmd/soong_ui/main.go
index 4aa62be..69e4f69 100644
--- a/cmd/soong_ui/main.go
+++ b/cmd/soong_ui/main.go
@@ -173,7 +173,6 @@
 	rbeMetricsFile := filepath.Join(logsDir, c.logsPrefix+"rbe_metrics.pb")
 	soongMetricsFile := filepath.Join(logsDir, c.logsPrefix+"soong_metrics")
 	defer build.UploadMetrics(buildCtx, config, c.simpleOutput, buildStarted, buildErrorFile, rbeMetricsFile, soongMetricsFile)
-	defer build.PrintGomaDeprecation(buildCtx, config)
 
 	os.MkdirAll(logsDir, 0777)
 	log.SetOutput(filepath.Join(logsDir, c.logsPrefix+"soong.log"))
diff --git a/ui/build/config.go b/ui/build/config.go
index e9a8fc9..9bd0877 100644
--- a/ui/build/config.go
+++ b/ui/build/config.go
@@ -24,6 +24,7 @@
 	"time"
 
 	"android/soong/shared"
+
 	"github.com/golang/protobuf/proto"
 
 	smpb "android/soong/ui/metrics/metrics_proto"
@@ -183,6 +184,17 @@
 		"EMPTY_NINJA_FILE",
 	)
 
+	if ret.UseGoma() {
+		ctx.Println("Goma for Android is being deprecated and replaced with RBE. See go/rbe_for_android for instructions on how to use RBE.")
+		ctx.Println()
+		ctx.Println("See go/goma_android_exceptions for exceptions.")
+		ctx.Fatalln("USE_GOMA flag is no longer supported.")
+	}
+
+	if ret.ForceUseGoma() {
+		ret.environ.Set("USE_GOMA", "true")
+	}
+
 	// Tell python not to spam the source tree with .pyc files.
 	ret.environ.Set("PYTHONDONTWRITEBYTECODE", "1")
 
@@ -778,6 +790,18 @@
 	return c.totalRAM
 }
 
+// ForceUseGoma determines whether we should override Goma deprecation
+// and use Goma for the current build or not.
+func (c *configImpl) ForceUseGoma() bool {
+	if v, ok := c.environ.Get("FORCE_USE_GOMA"); ok {
+		v = strings.TrimSpace(v)
+		if v != "" && v != "false" {
+			return true
+		}
+	}
+	return false
+}
+
 func (c *configImpl) UseGoma() bool {
 	if v, ok := c.environ.Get("USE_GOMA"); ok {
 		v = strings.TrimSpace(v)
diff --git a/ui/build/rbe.go b/ui/build/rbe.go
index c4b829d..182c544 100644
--- a/ui/build/rbe.go
+++ b/ui/build/rbe.go
@@ -151,13 +151,3 @@
 		ctx.Fatalf("failed to copy %q to %q: %v\n", metricsFile, filename, err)
 	}
 }
-
-// PrintGomaDeprecation prints a PSA on the deprecation of Goma if it is set for the build.
-func PrintGomaDeprecation(ctx Context, config Config) {
-	if config.UseGoma() {
-		fmt.Fprintln(ctx.Writer, "")
-		fmt.Fprintln(ctx.Writer, "Goma for Android is being deprecated and replaced with RBE.")
-		fmt.Fprintln(ctx.Writer, "See go/goma_android_deprecation for more details.")
-		fmt.Fprintln(ctx.Writer, "")
-	}
-}