[cmake] Generate CMakeArgs.txt file to store CMake src, build dir and invocation arguments

[sauravUppoor]

Fixes #811

This PR updates the CMakeLists.txt file with steps to store cmake command line arguments into a new file CMakeArgs.txt in the build directory.

Testing

Command

cmake -S ../clad -DClang_DIR=/home/saurav/Desktop/llvm-dev/build/ -DLLVM_DIR=/home/saurav/Desktop/llvm-dev/build/ -DCMAKE_INSTALL_PREFIX=../inst -DLLVM_EXTERNAL_LIT="$(which lit)" -B ../build

CMakeArgs.txt file content:

-S/home/saurav/Desktop/clad-dev/clad -B/home/saurav/Desktop/clad-dev/build  -DClang_DIR="/home/saurav/Desktop/llvm-dev/build/" -DLLVM_DIR="/home/saurav/Desktop/llvm-dev/build/" -DLLVM_EXTERNAL_LIT="/home/saurav/.local/bin/lit"

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.89%. Comparing base (48527c2) to head (096a252).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #815   +/-   ##
=======================================
  Coverage   94.89%   94.89%           
=======================================
  Files          49       49           
  Lines        7478     7478           
=======================================
  Hits         7096     7096           
  Misses        382      382           

[vgvassilev]

LGTM!