我在学习使用miniob。
在官方提供的容器forest中，执行build.sh出现以下问题
[ 12%] Building CXX object src/common/CMakeFiles/common.dir/time/timeout_info.cpp.o
[ 12%] Linking CXX static library …/…/lib/libcommon.a
make[2]: warning: Clock skew detected. Your build may be incomplete.
[ 12%] Built target common
[ 12%] generating lex and yacc files
flex: can’t open lex_sql.l
: cannot open: No such file or directory
make[2]: *** [src/observer/CMakeFiles/observer_static.dir/build.make:75: /root/miniob/src/observer/sql/parser/lex_sql.cpp] Error 1
make[1]: *** [CMakeFiles/Makefile2:332: src/observer/CMakeFiles/observer_static.dir/all] Error 2
make: *** [Makefile:146: all] Error 2
[ 12%] Built target common
[ 12%] generating lex and yacc files
flex: can’t open lex_sql.l
: cannot open: No such file or directory
make[2]: *** [src/observer/CMakeFiles/observer_static.dir/build.make:75: /root/miniob/src/observer/sql/parser/lex_sql.cpp] Error 1
make[1]: *** [CMakeFiles/Makefile2:332: src/observer/CMakeFiles/observer_static.dir/all] Error 2
make: *** [Makefile:146: all] Error 2
我检查过了flex与bison版本，
flex 2.6.4
bison (GNU Bison) 3.8.2
同时，我也确认了 lex_sql.l具有rwx权限。请问我该怎么做？