Contains two necessary changes for build success:
1. Move `DEBIAN_FRONTEND` to avoid timezone interaction. Current `ARG DEBIAN_FRONTEND` not seems to work.
2. Install `libfl-dev`, otherwise OpenSTA make will failed:
```
0.717 CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
0.717 Please set them or make sure they are set and tested correctly in the CMake files:
0.717 /OpenSTA/FLEX_INCLUDE_DIR
0.717 used as include directory in directory /OpenSTA
```
Signed-off-by: 王博伟 <wozluohd@gmail.com>
* Fixes#167
* No need to make app/ directory, it's already there
* Put lib/exe only in build dir, update docs and other references accordingly
* Remove gitignore stuff
* Bump CMake version too
* Minor correction to be more exact
* Update regression_vars.tcl
* Requested txt fixes
* Update date
王博伟
Akash Levy
James Cherry