Make it possible to debug soong_ui.

This works by setting the SOONG_UI_DELVE= environment variable to the
port on which soong_ui should accept a Delve connection on.

This is achieved by reusing the Delve execution logic between soong_ui
and soong_build.

Test: Manual.
Change-Id: Id2c1d4b6faac1a4a3918c91030ce2239f7daf54f

android/writedocs.go

@@ -66,7 +66,9 @@ func (c *docsSingleton) GenerateBuildActions(ctx SingletonContext) {
 	soongDocs := ctx.Rule(pctx, "soongDocs",
 		blueprint.RuleParams{
 			Command: fmt.Sprintf("rm -f ${outDir}/* && %s --soong_docs %s %s",
-				primaryBuilder.String(), docsFile.String(), strings.Join(os.Args[1:], " ")),
+				primaryBuilder.String(),
+				docsFile.String(),
+				"\""+strings.Join(os.Args[1:], "\" \"")+"\""),
 			CommandDeps: []string{primaryBuilder.String()},
 			Description: fmt.Sprintf("%s docs $out", primaryBuilder.Base()),
 		},