README.md: Replace meson_options.txt to meson.options

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I9db3af66deb7d3334be03606de61186e7a4e50cc
diff --git a/README.md b/README.md
index dde465b..1b6d403 100644
--- a/README.md
+++ b/README.md
@@ -7,8 +7,8 @@
 ## Configuration
 
 phosphor-time-manager is configured by setting `-D` flags that correspond to
-options in `phosphor-time-manager/meson_options.txt`. The option names become
-C++ preprocessor symbols that control which code is compiled into the program.
+options in `phosphor-time-manager/meson.options`. The option names become C++
+preprocessor symbols that control which code is compiled into the program.
 
 - Compile phosphor-time-manager with default options: