Build: fix failed to generate the executable file #9

[pandax381]

Fixed: Issue #9

linking pthread library:

$ make
...
Linking C executable ../bin/fluent-bit
[ 81%] Built target fluent-bit-bin
Scanning dependencies of target fluent-bit-shared
[ 84%] Building C object src/CMakeFiles/fluent-bit-shared.dir/flb_pack.c.o
[ 86%] Building C object src/CMakeFiles/fluent-bit-shared.dir/flb_input.c.o
[ 89%] Building C object src/CMakeFiles/fluent-bit-shared.dir/flb_output.c.o
[ 92%] Building C object src/CMakeFiles/fluent-bit-shared.dir/flb_config.c.o
[ 94%] Building C object src/CMakeFiles/fluent-bit-shared.dir/flb_network.c.o
[ 97%] Building C object src/CMakeFiles/fluent-bit-shared.dir/flb_utils.c.o
[100%] Building C object src/CMakeFiles/fluent-bit-shared.dir/flb_engine.c.o
Linking C shared library ../library/libfluent-bit.so
[100%] Built target fluent-bit-shared

Signed-off-by: Masaya YAMAMOTO <pandax381@gmail.com>

[edsiper]

thanks.