erofs-utils: correct --with-lz4 example in README

Option --with-lz4 means LZ4 install directory rather than LZ4 lib
directory. We will meet configuration error due to wrong path if
setting --with-lz4 to /usr/local/lib. Also stay the same with LZ4
help in configure shell script.

Signed-off-by: Yue Hu <huyue2@yulong.com>
Signed-off-by: Gao Xiang <hsiangkao@aol.com>
diff --git a/README b/README
index 9014268..97eb228 100644
--- a/README
+++ b/README
@@ -19,8 +19,8 @@
 
 How to build with lz4 static library
 	./configure --with-lz4=<lz4 install path>
-eg. if lz4 lib has been installed into fold of /usr/local/lib
-	./configure --with-lz4=/usr/local/lib && make
+eg. if lz4 has been installed into fold of /usr/local
+	./configure --with-lz4=/usr/local && make
 On Fedora, static lz4 can be installed using:
 	yum install lz4-static.x86_64
 To build you should run this first: