Exporting define for layer by layer profiler

Libraries that link the layer_by_layer_profiler interface library will
also get the LAYER_BY_LAYER_PROFILE define appending to the build
arguments. This allows the preprocessor to select which profiler to use.

Change-Id: I85fec66d2dd9949fd7fe395fb44e49bda1539925
diff --git a/lib/layer_by_layer_profiler/CMakeLists.txt b/lib/layer_by_layer_profiler/CMakeLists.txt
index 7a16da2..1e3d012 100644
--- a/lib/layer_by_layer_profiler/CMakeLists.txt
+++ b/lib/layer_by_layer_profiler/CMakeLists.txt
@@ -21,6 +21,17 @@
 endif()
 
 add_library(layer_by_layer_profiler INTERFACE)
-target_link_libraries(layer_by_layer_profiler INTERFACE ethosu_core_driver tflu event_recorder ethosu_log)
-target_include_directories(layer_by_layer_profiler INTERFACE include)
-target_sources(layer_by_layer_profiler INTERFACE src/layer_by_layer_profiler.cpp)
+
+target_link_libraries(layer_by_layer_profiler INTERFACE
+    ethosu_core_driver
+    tflu event_recorder
+    ethosu_log)
+
+target_include_directories(layer_by_layer_profiler INTERFACE
+    include)
+
+target_sources(layer_by_layer_profiler INTERFACE
+    src/layer_by_layer_profiler.cpp)
+
+target_compile_definitions(layer_by_layer_profiler INTERFACE
+    LAYER_BY_LAYER_PROFILER)