Fix the issue "\n" didn't get interpreted properly.

Added params to WriteFile rule that allow users to turn on the
specific 'echo' options, such as "enable the interpretation of backslash
escapes".

Bug: b/38261000
Test: tested with real data files.
Change-Id: I5145056b5c2522a3a72b9436055ec95d2fbd94c0

python/builder.go

@@ -82,7 +82,7 @@ func registerBuildActionForModuleFileList(ctx android.ModuleContext,
 		Output:      fileList,
 		Implicits:   files,
 		Args: map[string]string{
-			"content": strings.Join(content, "\n"),
+			"content": strings.Join(content, `\n`),
 		},
 	})