Fix compilation in MacOS

[rofafor]

The current master doesn't compile with my MacOS (Big Sur, XCode 12.3) setup.

Apple clang version 12.0.0 (clang-1200.0.32.28)
Target: x86_64-apple-darwin20.2.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

1. Missing include prevents compilation:

[ 44%] Building C object src/CMakeFiles/fluent-bit-static.dir/flb_coro.c.o
In file included from /Users/a113889/Code/workspace/rofa/fluent-bit/src/flb_coro.c:22:
/Users/a113889/Code/workspace/rofa/fluent-bit/include/fluent-bit/flb_thread_storage.h:48:8: error: unknown type name 'pthread_key_t'
extern FLB_TLS_DEFINE(struct flb_worker, flb_worker_ctx)
       ^
/Users/a113889/Code/workspace/rofa/fluent-bit/include/fluent-bit/flb_thread_storage.h:43:36: note: expanded from macro 'FLB_TLS_DEFINE'
#define FLB_TLS_DEFINE(type, name) pthread_key_t name;
                                   ^
1 error generated.
make[2]: *** [src/CMakeFiles/fluent-bit-static.dir/flb_coro.c.o] Error 1
make[1]: *** [src/CMakeFiles/fluent-bit-static.dir/all] Error 2
make: *** [all] Error 2

2. Wrong compiler flags prevents linking:

[ 84%] Linking C executable ../bin/fluent-bit
duplicate symbol '_mk_tls_cache_gmtext' in:
    ../library/libfluent-bit.a(flb_config.c.o)
    ../library/libfluent-bit.a(flb_engine.c.o)
...
duplicate symbol '_mk_tls_sched_worker_node' in:
    ../library/libfluent-bit.a(flb_config.c.o)
    ../lib/monkey/library/monkey-liana.a(liana.c.o)
ld: 420 duplicate symbols for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [bin/fluent-bit] Error 1
make[1]: *** [src/CMakeFiles/fluent-bit-bin.dir/all] Error 2
make: *** [all] Error 2

---

Enter [N/A] in the box, if an item is not applicable to your change.

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

Documentation

• [N/A] Documentation required for this feature

---

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.

[bluebike]

PR worked in macOS catalina (10.15)

Just had to export MACOSX_DEPLOYMENT_TARGET=10.15

Note. In my case, if I have /usr/local/bin (with homebrew stuff) in beginning of PATH, make fails. Has been same all the time... strange.

[edsiper]

thanks!