Building with a recent compiler fails due incompatible expected library (BehaviorTree#833)

* >Fixes build with newer clang/gcc

* >Fixes build with newer clang/gcc

* conditional build of sample nodes

* using current head version for testing

* moved to v0.8.0

Author: psyinf

CMakeLists.txt

@@ -198,7 +198,9 @@ message( STATUS "BTCPP_LIB_DESTINATION:   ${BTCPP_LIB_DESTINATION} " )
 message( STATUS "BTCPP_INCLUDE_DESTINATION: ${BTCPP_INCLUDE_DESTINATION} " )
 message( STATUS "BTCPP_UNIT_TESTS:   ${BTCPP_UNIT_TESTS} " )
 
+if (BTCPP_UNIT_TESTS OR BTCPP_EXAMPLES) 
 add_subdirectory(sample_nodes)
+endif()
 
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