fix: log runtime output to env var "BPFTIME_LOG_OUTPUT"

[Kailian-Jacy]

Description

A draft version of logging. It implements:

• Log spdlogs to target from env var BPFTIME_LOG_OUTPUT. Default to be stderr. All logs from runtime (syscall_server, agent, agent-transformer) go to given target.
• Logs from client (cli/main.cpp) and ebpf program output untouched. I suppose ppl always want client feedback from stdout/err.

Used file but not named pipe. bpftime server should be similar to docker daemon, managing "services" of injected ebpf programs. The log should be persistent, reusable.

Now usage:

kailian@ubt23:~/bpftime$ sudo BPFTIME_LOG_OUTPUT=skeleton_logging.out /home/kailian/.bpftime/bpftime -i /home/kailian/.bpftime load ./example/opensnoop/opensnoop\
PID    COMM              FD ERR PATH
^CINFO [40749]: Global shm destructed

kailian@ubt23:~/bpftime$ cat skeleton_logging.out
[2024-06-02 10:12:32][info][40749] manager constructed
[2024-06-02 10:12:32][info][40749] Initialize syscall server
[2024-06-02 10:12:32][info][40749] Global shm constructed. shm_open_type 0 for bpftime_maps_shm
[2024-06-02 10:12:32][info][40749] Global shm initialized
[2024-06-02 10:12:32][info][40749] Enabling helper groups ufunc, kernel, shm_map by default
[2024-06-02 10:12:32][info][40749] bpftime-syscall-server started

I may add these feature in this PR, hoping suggestions or confirmation from you:

• Provide a subcommand similar to trace to output logs we want.
• Logs be optionally reserved under /var/log/ or syslog under linux. Log rotation are management automatically.
• Merge logs from different processes as one. Add tags of source (which injected process causing) to the log.
• Add documentations about logging.

resolves # 279

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] This change requires a documentation update

How Has This Been Tested?

• [x] Manually test: load & start.

sudo BPFTIME_LOG_OUTPUT=skeleton_logging.out /home/kailian/.bpftime/bpftime -i /home/kailian/.bpftime load ./example/opensnoop/opensnoop
sudo BPFTIME_LOG_OUTPUT=skeleton_logging.out /home/kailian/.bpftime/bpftime -i /home/kailian/.bpftime start  ./example/opensnoop/victim
sudo BPFTIME_LOG_OUTPUT=skeleton_logging.out /home/kailian/.bpftime/bpftime -i /home/kailian/.bpftime start  -s ./example/opensnoop/victim

• [x] Manually test: load & attach.

sudo BPFTIME_LOG_OUTPUT=victim_out.log ./example/opensnoop/victim
sudo BPFTIME_LOG_OUTPUT=skeleton_logging.out /home/kailian/.bpftime/bpftime -i /home/kailian/.bpftime attach `pidof victim`

Test Configuration:

• Hardware: x86
• Toolchain:g++
• OS: ubuntu 23.10

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules
• [x] I have checked my code and corrected any misspellings

[yunwei37]

Also:

1. Fix compile for build without libbpf in Linux
2. Add option build test in CI