error when building the macos option [6]

running step 6 of the `build.py` gives the following error:

```
make[2]: *** No rule to make target `../../v8.out//libv8_monolith.a', needed by `libj2v8-macosx-x86_64.dylib'. Stop.
make[2]: *** Waiting for unfinished jobs....
```

Full output:

```
python2 build.py -i

entering interactive mode...

[0] android-x86 @ Docker
[1] android-arm @ Docker
[2] alpine-linux-x64 @ Docker
[3] linux-x64
[4] linux-x64 @ Docker
[5] linux-x86 @ Docker
[6] macosx-x64
[7] macosx-x64 @ Vagrant
[8] macosx-x86 @ Vagrant
[9] windows-x64
[10] windows-x64 @ Docker
[11] windows-x64 @ Vagrant

Select a predefined build-configuration to run: 6
Building: macosx-x64

Override build-steps ? (leave empty to run pre-configured steps):
WARNING: skipping build step "v8" (not configured and/or supported for platform "macos")
GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin19)
Copyright (C) 2007 Free Software Foundation, Inc.
Updating Maven configuration (./docker/shared/pom.xml)...
SHELL building macos@x64 => j2v8cmake
-- The C compiler identification is AppleClang 11.0.3.11030032
-- The CXX compiler identification is AppleClang 11.0.3.11030032
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Java version 1.8.0.181 found!
Using Java-Root: /Library/Java/JavaVirtualMachines/graalvm-ce-java11-20.1.0/Contents/Home
--------------------------------------------------
J2V8_LIB_ARCH_NAME = x86_64
J2V8_LIB_VENDOR_NAME =
J2V8_LIB_PLATFORM_NAME = macosx
J2V8_TARGET_ARCH = x86_64
J2V8_BUILD_X64 = TRUE
--------------------------------------------------
-- Configuring done
-- Generating done
CMake Warning:
Manually-specified variables were not used by the project:

J2V8_NODE_ENABLED

-- Build files have been written to: /Users/chris/Desktop/j2v8/J2V8-master/cmake.out/macos.x64
GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin19)
Copyright (C) 2007 Free Software Foundation, Inc.
Updating Maven configuration (./docker/shared/pom.xml)...
SHELL building macos@x64 => j2v8jni
Generating JNI header files...
Done
GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin19)
Copyright (C) 2007 Free Software Foundation, Inc.
Updating Maven configuration (./docker/shared/pom.xml)...
SHELL building macos@x64 => j2v8cpp
/usr/local/Cellar/cmake/3.19.1/bin/cmake -S/Users/chris/Desktop/j2v8/J2V8-master -B/Users/chris/Desktop/j2v8/J2V8-master/cmake.out/macos.x64 --check-build-system CMakeFiles/Makefile.cmake 0
/usr/local/Cellar/cmake/3.19.1/bin/cmake -E cmake_progress_start /Users/chris/Desktop/j2v8/J2V8-master/cmake.out/macos.x64/CMakeFiles /Users/chris/Desktop/j2v8/J2V8-master/cmake.out/macos.x64//CMakeFiles/progress.marks
/Applications/Xcode.app/Contents/Developer/usr/bin/make -f CMakeFiles/Makefile2 all
/Applications/Xcode.app/Contents/Developer/usr/bin/make -f CMakeFiles/j2v8.dir/build.make CMakeFiles/j2v8.dir/depend
cd /Users/chris/Desktop/j2v8/J2V8-master/cmake.out/macos.x64 && /usr/local/Cellar/cmake/3.19.1/bin/cmake -E cmake_depends "Unix Makefiles" /Users/chris/Desktop/j2v8/J2V8-master /Users/chris/Desktop/j2v8/J2V8-master /Users/chris/Desktop/j2v8/J2V8-master/cmake.out/macos.x64 /Users/chris/Desktop/j2v8/J2V8-master/cmake.out/macos.x64 /Users/chris/Desktop/j2v8/J2V8-master/cmake.out/macos.x64/CMakeFiles/j2v8.dir/DependInfo.cmake --color=
Scanning dependencies of target j2v8
/Applications/Xcode.app/Contents/Developer/usr/bin/make -f CMakeFiles/j2v8.dir/build.make CMakeFiles/j2v8.dir/build
make[2]: *** No rule to make target `../../v8.out//libv8_monolith.a', needed by `libj2v8-macosx-x86_64.dylib'. Stop.
make[2]: *** Waiting for unfinished jobs....
[ 50%] Building CXX object CMakeFiles/j2v8.dir/jni/com_eclipsesource_v8_V8Impl.cpp.o
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ -Dj2v8_EXPORTS -I/Users/chris/Desktop/j2v8/J2V8-master/v8.out/include -I/Library/Java/JavaVirtualMachines/graalvm-ce-java11-20.1.0/Contents/Home/include -I/Library/Java/JavaVirtualMachines/graalvm-ce-java11-20.1.0/Contents/Home/include/darwin -O3 -DNDEBUG -arch x86_64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk -fPIC -std=gnu++14 -o CMakeFiles/j2v8.dir/jni/com_eclipsesource_v8_V8Impl.cpp.o -c /Users/chris/Desktop/j2v8/J2V8-master/jni/com_eclipsesource_v8_V8Impl.cpp
/Users/chris/Desktop/j2v8/J2V8-master/jni/com_eclipsesource_v8_V8Impl.cpp:357:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
object->Set(context, v8Key, value);
^~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~
/Users/chris/Desktop/j2v8/J2V8-master/jni/com_eclipsesource_v8_V8Impl.cpp:858:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
(*script)->Run(context);
^~~~~~~~~~~~~~ ~~~~~~~
/Users/chris/Desktop/j2v8/J2V8-master/jni/com_eclipsesource_v8_V8Impl.cpp:1474:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
array->Set(context, index, Null(isolate));
^~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/chris/Desktop/j2v8/J2V8-master/jni/com_eclipsesource_v8_V8Impl.cpp:1488:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
array->Set(context, index, Undefined(isolate));
^~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/chris/Desktop/j2v8/J2V8-master/jni/com_eclipsesource_v8_V8Impl.cpp:1504:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
array->Set(context, index, v8Value);
^~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~
/Users/chris/Desktop/j2v8/J2V8-master/jni/com_eclipsesource_v8_V8Impl.cpp:1519:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
array->Set(context, index, v8Value);
^~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~
/Users/chris/Desktop/j2v8/J2V8-master/jni/com_eclipsesource_v8_V8Impl.cpp:1534:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
array->Set(context, index, v8Value);
^~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~
/Users/chris/Desktop/j2v8/J2V8-master/jni/com_eclipsesource_v8_V8Impl.cpp:1549:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
array->Set(context, index, v8Value);
^~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~
/Users/chris/Desktop/j2v8/J2V8-master/jni/com_eclipsesource_v8_V8Impl.cpp:1564:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
array->Set(context, index, v8Value);
^~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~
/Users/chris/Desktop/j2v8/J2V8-master/jni/com_eclipsesource_v8_V8Impl.cpp:1918:3: warning: ignoring return value of function declared with 'warn_unused_result' attribute [-Wunused-result]
object->SetPrototype(context, prototype);
^~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~
10 warnings generated.
make[1]: *** [CMakeFiles/j2v8.dir/all] Error 2
make: *** [all] Error 2
Traceback (most recent call last):
File "build.py", line 13, in
interactive.run_interactive_cli()
File "/Users/chris/Desktop/j2v8/J2V8-master/build_system/build_interactive.py", line 58, in run_interactive_cli
bex.execute_build(build_params)
File "/Users/chris/Desktop/j2v8/J2V8-master/build_system/build_executor.py", line 322, in execute_build
execute_build_step(target_compiler, target_step)
File "/Users/chris/Desktop/j2v8/J2V8-master/build_system/build_executor.py", line 231, in execute_build_step
build_system.build(build_step)
File "/Users/chris/Desktop/j2v8/J2V8-master/build_system/build_structures.py", line 96, in build
self.exec_build(config)
File "/Users/chris/Desktop/j2v8/J2V8-master/build_system/shell_build.py", line 27, in exec_build
self.exec_cmd(shell_str, config)
File "/Users/chris/Desktop/j2v8/J2V8-master/build_system/build_structures.py", line 113, in exec_cmd
self.__exec_cmd_core(cmd, config, config.build_cwd)
File "/Users/chris/Desktop/j2v8/J2V8-master/build_system/build_structures.py", line 122, in __exec_cmd_core
utils.execute(cmd, cwd)
File "/Users/chris/Desktop/j2v8/J2V8-master/build_system/build_utils.py", line 157, in execute
raise subprocess.CalledProcessError(return_code, cmd)
subprocess.CalledProcessError: Command 'cd /Users/chris/Desktop/j2v8/J2V8-master && cd ./cmake.out/macos.x64/ && make -j4' returned non-zero exit status 2
```