Merge "Set download_tmp_dir explicitly to be a directory under the output directory." into main

ui/build/config.go

@@ -1349,6 +1349,19 @@ func (c *configImpl) rbeProxyLogsDir() string {
 			return v
 		}
 	}
+	return c.rbeTmpDir()
+}
+
+func (c *configImpl) rbeDownloadTmpDir() string {
+    for _, f := range []string{"RBE_download_tmp_dir", "FLAG_download_tmp_dir"} {
+		if v, ok := c.environ.Get(f); ok {
+			return v
+		}
+	}
+	return c.rbeTmpDir()
+}
+
+func (c *configImpl) rbeTmpDir() string {
 	buildTmpDir := shared.TempDirForOutDir(c.SoongOutDir())
 	return filepath.Join(buildTmpDir, "rbe")
 }

ui/build/rbe.go

@@ -61,6 +61,7 @@ func getRBEVars(ctx Context, config Config) map[string]string {
 		"RBE_output_dir":       config.rbeProxyLogsDir(),
 		"RBE_proxy_log_dir":    config.rbeProxyLogsDir(),
 		"RBE_cache_dir":        config.rbeCacheDir(),
+		"RBE_download_tmp_dir": config.rbeDownloadTmpDir(),
 		"RBE_platform":         "container-image=" + remoteexec.DefaultImage,
 	}
 	if config.StartRBE() {