Let the test applications be left out with ROCTRACER_BUILD_TESTS=OFF. They are built
whether or not tests are asked for, and they need a HIP compiler and GPU headers.

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -65,7 +65,8 @@
 add_subdirectory(src)
 
 ## Build tests
-if(${LIBRARY_TYPE} STREQUAL SHARED)
+option(ROCTRACER_BUILD_TESTS "build the test applications" ON)
+if(${LIBRARY_TYPE} STREQUAL SHARED AND ROCTRACER_BUILD_TESTS)
   add_subdirectory(test)
 endif()