runtime: make LLVM JIT Compiled by default

[NobinPegasus]

Description

Fixes #262 (issue)

Type of change

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

How Has This Been Tested?

cmake -DCMAKE_PREFIX_PATH=/usr/include/llvm -DBPFTIME_LLVM_JIT=YES -DBPFTIME_ENABLE_UNIT_TESTING=YES -DCMAKE_BUILD_TYPE=Release -B build
cmake --build build --config RelWithDebInfo --target bpftime_runtime_tests
sudo ./build/runtime/unit-test/bpftime_runtime_tests

Log:

bpftime_runtime_tests is a Catch2 v3.4.0 host application.
Run with -? for options

-------------------------------------------------------------------------------
Test tail calling from userspace to kernel
-------------------------------------------------------------------------------
/workdir/bpftime/runtime/unit-test/tailcall/test_user_to_kernel_tailcall.cpp:18
...............................................................................

/workdir/bpftime/runtime/unit-test/tailcall/test_user_to_kernel_tailcall.cpp:26: FAILED:
  REQUIRE( map_fd >= 0 )
with expansion:
  -1 >= 0

===============================================================================
test cases:   15 |   14 passed | 1 failed
assertions: 4088 | 4087 passed | 1 failed

Test Configuration: I have used the docker image to rebuild using updated cmake and makeflie. Because the project is LLVM Version dependent.

root@3fe2301ad245:/workdir/bpftime# llvm-config --version
15.0.7
root@3fe2301ad245:/workdir/bpftime# clang --version
Ubuntu clang version 15.0.7
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

root@3fe2301ad245:/workdir/bpftime# cat /etc/os-release 
PRETTY_NAME="Ubuntu 23.04"
NAME="Ubuntu"
VERSION_ID="23.04"
VERSION="23.04 (Lunar Lobster)"
VERSION_CODENAME=lunar
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
UBUNTU_CODENAME=lunar
LOGO=ubuntu-logo

Checklist

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

[yunwei37]

Thanks!