llcppsigfetch:abs include path & system header & config mode 's include flags

[luoliwoshang]

• Change includes to output absolute paths for corresponding header files
• Identify system header files
• std include path
• config mode 's include flags

  {
  "incPath": "stddef.h",
  "isSys": true,
  "path": "/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk/usr/include/stddef.h",
  "doc": {
    "_Type": "File",
    "includes": [
      {
        "_Type": "Include",
        "Path": "/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk/usr/include/_types.h"
      },
      {
        "_Type": "Include",
        "Path": "/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk/usr/include/sys/_types/_size_t.h"
      },
    ],
  },
  {
  "incPath": "sys/_types/_size_t.h",
  "path": "/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk/usr/include/sys/_types/_size_t.h",
  "doc": {
    "_Type": "File",
    "includes": [
      {
        "_Type": "Include",
        "Path": "/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk/usr/include/machine/_types.h"
      }
    ],
  },
  "isSys": true
  },
  },

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.69%. Comparing base (e042aad) to head (289a443). Report is 58 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #853 +/- ## ========================================== + Coverage 95.53% 95.69% +0.15% ========================================== Files 22 22 Lines 6230 6249 +19 ========================================== + Hits 5952 5980 +28 + Misses 246 242 -4 + Partials 32 27 -5 ```

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[luoliwoshang]

@xushiwei ready for review