build shared lib only if BUILD_SHARED_LIBS is set (#34)

Co-authored-by: Hannes Harms <h.harms@grimme.de>

CMakeLists.txt

@@ -7,6 +7,7 @@ option(FORCE_BUILD_VENDOR_PKG
   OFF)
 
 find_package(ament_cmake REQUIRED)
+ament_add_default_options()
 
 macro(build_yaml_cpp)
   set(extra_cmake_args)
@@ -22,7 +23,9 @@ macro(build_yaml_cpp)
   list(APPEND extra_cmake_args "-DYAML_CPP_BUILD_TESTS=OFF")
   list(APPEND extra_cmake_args "-DYAML_CPP_BUILD_TOOLS=OFF")
   list(APPEND extra_cmake_args "-DYAML_CPP_BUILD_CONTRIB=OFF")
-  list(APPEND extra_cmake_args "-DYAML_BUILD_SHARED_LIBS=ON")
+  if(BUILD_SHARED_LIBS)
+    list(APPEND extra_cmake_args "-DYAML_BUILD_SHARED_LIBS=ON")
+  endif()
   list(APPEND extra_cmake_args "-DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}")
   list(APPEND extra_cmake_args "-DCMAKE_CXX_FLAGS=${CMAKE_CXX_FLAGS}")