[tools](tpcds) Update README.md, use default gcc

compile with gcc-11 is not ok,
compile with gcc 9.40 or below is ok,
default gcc often meet requirements.

tools/tpcds-tools/README.md

@@ -24,6 +24,7 @@ follow the steps below:
 
 ### 1. build tpc-ds dsdgen dsqgen tool.
 
+    export PATH=/usr/bin/:$PATH
     ./bin/build-tpcds-tools.sh
 
 ### 2. generate tpc-ds data. use -h for more infomations.