fix: remove Debian LLVM PPA repo (Linux runners only)

[2bndy5]

resolves #265

Users that expect the PPA to be present after running cpp-linter-action can set the environment variable KEEP_DEBIAN_LLVM_PPA to true, on, or 1. By default, the PPA is removed.

[github-actions]

Cpp-Linter Report ⚠️

Some files did not pass the configured checks!

clang-format (v12.0.0) reports: 2 file(s) not formatted

• docs/examples/demo/demo.cpp
• docs/examples/demo/demo.hpp

clang-tidy (v12.0.0) reports: 7 concern(s)

• docs/examples/demo/demo.cpp:3:10: warning: [modernize-deprecated-headers]

  inclusion of deprecated C++ header 'stdio.h'; consider using 'cstdio' instead

  #include <stdio.h>
           ^~~~~~~~~
           <cstdio>

• docs/examples/demo/demo.cpp:8:5: warning: [modernize-use-trailing-return-type]

  use a trailing return type for this function

  int main(){
  ~~~ ^
  auto       -> int

• docs/examples/demo/demo.cpp:10:13: warning: [readability-braces-around-statements]

  statement should be inside braces

      for (;;) break;
              ^
               {

• docs/examples/demo/demo.cpp:13:5: warning: [cppcoreguidelines-pro-type-vararg]

  do not call c-style vararg functions

      printf("Hello world!\n");
      ^

• docs/examples/demo/demo.hpp:6:11: warning: [modernize-use-default-member-init]

  use default member initializer for 'useless'

      char* useless;
            ^
                   {"\0"}

• docs/examples/demo/demo.hpp:7:9: warning: [modernize-use-default-member-init]

  use default member initializer for 'numb'

      int numb;
          ^
              {0}

• docs/examples/demo/demo.hpp:11:11: warning: [modernize-use-trailing-return-type]

  use a trailing return type for this function

      void *not_useful(char *str){useless = str;}
      ~~~~~~^
      auto                        -> void *

Have any feedback or feature suggestions? Share it here.

[2bndy5]

I don't intend to get this out in the next release. I still want to test this in the test repo to be sure there is no undesired behavior or side effects.

[shenxianpeng]

Totally agree. As more people use it, any undesired behavior or side effects will block user work.