Build error when -DBUILD_EXAMPLES=False

[Yadunund]

Greetings,

I tried building the latest master with -DBUILD_EXAMPLES=False and I encounter the error below

/usr/bin/ld: cannot find -lbt_sample_nodes
collect2: error: ld returned 1 exit status
make[2]: *** [tests/CMakeFiles/behaviortree_cpp_v3_test.dir/build.make:284: tests/behaviortree_cpp_v3_test] Error 1
make[1]: *** [CMakeFiles/Makefile2:227: tests/CMakeFiles/behaviortree_cpp_v3_test.dir/all] Error 2
make: *** [Makefile:141: all] Error 2

This happens since lib bt_samples_nodes is only built when BUILD_EXAMPLES is enabled but is linked to the tests which gets built regardless

Instructions to reproduce error:

git clone https://github.com/BehaviorTree/BehaviorTree.CPP.git
cd BehaviorTree.CPP
mkdir build && cd build
cmake .. -DBUILD_EXAMPLES=False
make

[asasine]

This change causes the tests to no longer be built by default. Should the default value for BUILD_SAMPLES be set to ON?