build: use the system provided LuaJIT if found

[ThomasDevoogdt]

e.g. buildroot has logic to build luajit,
so if pkg_check_modules can find a suitable version, then use that one

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Testing
Before we can approve your change; please submit the following in a comment:

• [N/A] Example configuration file for the change
• [N/A] Debug log output from testing the change

• [N/A] Attached Valgrind output that shows no leaks or memory corruption was found

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• [N/A] Run local packaging test showing all targets (including any new ones) build.
• Set ok-package-test label to test for all targets (requires maintainer to do).

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• [N/A] Documentation required for this feature

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• Backport to latest stable release.

---

Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

[ScarletTanager]

Hi @cosmo0920 , this PR is really important for us to leverage fluentbit on zLinux (s390x), as we make extensive use of Lua in our configurations.

/cc @edsiper @celalettin1286 @fujimotos @koleini @leonardo-albertovich @niedbalski @patrick-stephens @agup006

[cosmo0920]

Hi, any chance to add the following workflows in https://github.com/fluent/fluent-bit/blob/master/.github/workflows/pr-compile-check.yaml?

  # Sanity check for compilation using system libraries
  pr-compile-system-libs:
    runs-on: ubuntu-20.04
    timeout-minutes: 60
    strategy:
      fail-fast: false
      matrix:
        flb_option:
          - "-DFLB_PREFER_SYSTEM_LIBS=On"
        compiler:
          - gcc
          - clang
    steps:
      - name: Setup environment
        run: |
          sudo apt-get update
          sudo apt-get install -y gcc-7 g++-7 clang-6.0 libsystemd-dev gcovr libyaml-dev libluajit-5.1-dev
          sudo ln -s /usr/bin/llvm-symbolizer-6.0 /usr/bin/llvm-symbolizer || true

      - name: Checkout Fluent Bit code
        uses: actions/checkout@v4

      - name: ${{ matrix.compiler }} - ${{ matrix.flb_option }}
        run: |
          export nparallel=$(( $(getconf _NPROCESSORS_ONLN) > 8 ? 8 : $(getconf _NPROCESSORS_ONLN) ))
          echo "CC = $CC, CXX = $CXX, FLB_OPT = $FLB_OPT"
          sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-7 90
          sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-7 90
          sudo update-alternatives --install /usr/bin/clang clang /usr/bin/clang-6.0 90
          cmake $GLOBAL_OPTS $FLB_OPT  ../
          make -j $nparallel
        working-directory: build
        env:
          CC: ${{ matrix.compiler }}
          CXX: ${{ matrix.compiler }}
          FLB_OPT: ${{ matrix.flb_option }}
          GLOBAL_OPTS: "-DFLB_BACKTRACE=Off -DFLB_SHARED_LIB=Off -DFLB_DEBUG=On -DFLB_ALL=On -DFLB_EXAMPLES=Off"

      - name: Display dependencies w/ ldd
        run: |
          ldd ./bin/fluent-bit
        working-directory: build

This would be good to add to verify every time whether buildable or not with prefer system libs flag.

I tested the above workflow in my fluent-bit fork and works fine:

Run ldd ./bin/fluent-bit
	linux-vdso.so.1 (0x00007ffc[4](https://github.com/cosmo0920/fluent-bit/actions/runs/9788101299/job/27025620765#step:5:5)b1f1000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007ffa7869c000)
	librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007ffa78692000)
	libluajit-[5](https://github.com/cosmo0920/fluent-bit/actions/runs/9788101299/job/27025620765#step:5:6).1.so.2 => /lib/x86_64-linux-gnu/libluajit-5.1.so.2 (0x00007ffa78617000)
	libyaml-0.so.2 => /lib/x8[6](https://github.com/cosmo0920/fluent-bit/actions/runs/9788101299/job/27025620765#step:5:7)_64-linux-gnu/libyaml-0.so.2 (0x00007ffa785f5000)
	libsystemd.so.0 => /lib/x86_64-linux-gnu/libsystemd.so.0 (0x0000[7](https://github.com/cosmo0920/fluent-bit/actions/runs/9788101299/job/27025620765#step:5:8)ffa78546000)
	libssl.so.1.1 => /lib/x86_64-linux-gnu/libssl.so.1.1 (0x00007ffa784b3000)
	libcrypto.so.1.1 => /lib/x[8](https://github.com/cosmo0920/fluent-bit/actions/runs/9788101299/job/27025620765#step:5:9)6_64-linux-gnu/libcrypto.so.1.1 (0x00007ffa781da000)
	libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007ffa781be000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007ffa7806f000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007ffa7806[9](https://github.com/cosmo0920/fluent-bit/actions/runs/9788101299/job/27025620765#step:5:10)000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007ffa77e77000)
	/lib64/ld-linux-x86-64.so.2 (0x00007ffa786d[10](https://github.com/cosmo0920/fluent-bit/actions/runs/9788101299/job/27025620765#step:5:11)00)
	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007ffa77e5c000)
	liblzma.so.5 => /lib/x86_64-linux-gnu/liblzma.so.5 (0x00007ffa77e31000)
	liblz4.so.1 => /lib/x86_64-linux-gnu/liblz4.so.1 (0x00007ffa77e10000)
	libgcrypt.so.20 => /lib/x86_64-linux-gnu/libgcrypt.so.20 (0x00007ffa77cf2000)
	libgpg-error.so.0 => /lib/x86_64-linux-gnu/libgpg-error.so.0 (0x00007ffa77ccf000)

ref: https://github.com/cosmo0920/fluent-bit/actions/runs/9788101299/job/27025620765

[ThomasDevoogdt]

Hi, any chance to add the following workflows in https://github.com/fluent/fluent-bit/blob/master/.github/workflows/pr-compile-check.yaml?

I've pushed a commit with your commit proposal.

[ThomasDevoogdt]

@cosmo0920 I've rebased the PR, the checks are now green again.

[rightblank]

Hi, @edsiper @cosmo0920, @patrick-stephens, is there any further blocker for merging this PR? If not, would you please help to merge it?

[ThomasDevoogdt]

@cosmo0920, @patrick-stephens, is there any further blocker for merging this PR? If not, would you please help to merge it?

I guess it's @edsiper you have to ping.

[ThomasDevoogdt]

@edsiper @cosmo0920 kind ping

[ThomasDevoogdt]

@edsiper kind remember

[cosmo0920]

@edsiper Can we include this PR in the v3.1.5 milestone?

[rightblank]

Hi, @ThomasDevoogdt, would you please help to merge ThomasDevoogdt#13 so that the feature in this PR can be enabled on the s390x architecture? Thanks!

[edsiper]

@ThomasDevoogdt thanks for the contribution!. Would you please submit a PR for fluent-bit-docs so we can reflect these new feature at build time ?

[rightblank]

Hi, @edsiper , would you please help to review #9172 which depends on this PR and further enable it on s390x?