tracing: avoid building tracing code when not applicable

Do not build tracing system if provided otherwise, for example right now
systemview does not need any of the zephyr interfaces.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

subsys/tracing/CMakeLists.txt

@@ -6,12 +6,12 @@ zephyr_sources_ifdef(
   )
 
 zephyr_sources_ifdef(
-  CONFIG_TRACING
+  CONFIG_TRACING_CORE
   tracing_buffer.c
   tracing_core.c
   tracing_format_common.c
   )
-
+if(CONFIG_TRACING_CORE)
 zephyr_sources_ifdef(
   CONFIG_TRACING_SYNC
   tracing_format_sync.c
@@ -36,6 +36,7 @@ zephyr_sources_ifdef(
   CONFIG_TRACING_BACKEND_POSIX
   tracing_backend_posix.c
   )
+endif()
 
 zephyr_include_directories_ifdef(
   CONFIG_TRACING

subsys/tracing/Kconfig

@@ -16,6 +16,11 @@ config TRACING
 
 if TRACING
 
+config TRACING_CORE
+	bool
+	help
+	  Automatically selected by formats that require the core
+	  tracing infrastructure.
 
 choice
 	prompt "Tracing Format"
@@ -32,18 +37,15 @@ config SEGGER_SYSTEMVIEW
 	select RTT_CONSOLE
 	select USE_SEGGER_RTT
 
-config TRACING_SYSTEMVIEW
-	bool "Tracing via SEGGER Systemview support"
-	help
-	  Enable tracing using SEGGER Systemview.
-
 config TRACING_CTF
 	bool "Tracing via Common Trace Format support"
+	select TRACING_CORE
 	help
 	  Enable tracing to a Common Trace Format stream.
 
 config TRACING_CPU_STATS
 	bool "Enable CPU usage tracing"
+	select TRACING_CORE
 	help
 	  Module provides information about percent of CPU usage based on
 	  tracing hooks for threads switching in and out, interrupts enters
@@ -53,6 +55,7 @@ config TRACING_CPU_STATS
 
 config TRACING_TEST
 	bool "Tracing for test usage"
+	select TRACING_CORE
 	help
 	  Enable tracing for testing kinds of format purpose. It must
 	  implement the tracing hooks defined in tracing_test.h