fluent-bit: build: bundled LuaJIT generate invalid .a file on macOS

System information

• macOS 12.3.1
• architecture: arm64 (M1)

Command-line tools

 clang --version                                                                                       
Apple clang version 13.1.6 (clang-1316.0.21.2.3)
Target: arm64-apple-darwin21.4.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

note: XCode is not installed, just command line tools

Issue

when trying to compile Fluent Bit, the linker complains about the object .a generated by the bundled LuaJIT:

[100%] Linking C shared library ../lib/libfluent-bit.dylib
ld: warning: ignoring file ../lib/libluajit.a, building for macOS-arm64 but attempting to link with file built for
 unknown-unsupported file format ( 0x21 0x3C 0x61 0x72 0x63 0x68 0x3E 0x0A 0x2F 0x20 0x20 0x20 0x20 0x20 0x20 0x20 )
Undefined symbols for architecture arm64:
  "_luaL_loadfile", referenced from:
      _flb_luajit_load_script in libfluent-bit.a(flb_luajit.c.o)
  "_luaL_newstate", referenced from:
      _flb_luajit_create in libfluent-bit.a(flb_luajit.c.o)
  "_luaL_openlibs", referenced from:
      _flb_luajit_create in libfluent-bit.a(flb_luajit.c.o)

Inspecting the file generated lib/libluajit.a we can see it has something wrong with it:

 » lipo -info lib/libluajit.a                                                                            
fatal error: /Library/Developer/CommandLineTools/usr/bin/lipo: archive with no architecture specification: lib/libluajit.a (can't determine architecture for it)

there is something wrong with our CMake rules, because if we take the same LuaJIT code and we build it with make (outside of Fluent Bit context), it builds just fine:

~/coding/LuaJIT (v2.1) » make                                                                                                                   edsiper@monox
==== Building LuaJIT 2.1.0-beta3 ====
/Library/Developer/CommandLineTools/usr/bin/make -C src
HOSTCC    host/minilua.o
HOSTLINK  host/minilua
DYNASM    host/buildvm_arch.h
HOSTCC    host/buildvm.o
HOSTCC    host/buildvm_asm.o
HOSTCC    host/buildvm_peobj.o
HOSTCC    host/buildvm_lib.o
HOSTCC    host/buildvm_fold.o
HOSTLINK  host/buildvm
BUILDVM   lj_vm.S
ASM       lj_vm.o
CC        lj_assert.o
CC        lj_gc.o
BUILDVM   lj_ffdef.h
CC        lj_err.o
CC        lj_char.o
BUILDVM   lj_bcdef.h
CC        lj_bc.o
....
AR        libluajit.a
CC        luajit.o
BUILDVM   jit/vmdef.lua
DYNLINK   libluajit.so
LINK      luajit
OK        Successfully built LuaJIT
==== Successfully built LuaJIT 2.1.0-beta3 ====
--------------------------------------------------------------------------------------------------------------------------------------------------------------
~/coding/LuaJIT (v2.1) » lipo -info src/libluajit.a                                                                                             edsiper@monox
Non-fat file: src/libluajit.a is architecture: arm64
-----------------------------

lipo tool returns the expected file format for the .a file.

Our LuaJIT build rules are in this file:

• https://github.com/fluent/fluent-bit/blob/master/cmake/luajit.cmake

notes:

• no XCODE here
• no binutils
• using the latest xcode command line tools
• already tried different flags, same issue

any macOS wizard who can assist here ?