cmake init, printChar tests

serviceinterface/CMakeLists.txt

@@ -0,0 +1,5 @@
+target_sources(${LIB_FSFW_NAME} 
+	PRIVATE 
+		ServiceInterfaceStream.cpp
+		ServiceInterfaceBuffer.cpp
+)

serviceinterface/ServiceInterfaceBuffer.cpp

@@ -4,7 +4,7 @@
 #include <inttypes.h>
 
 // to be implemented by bsp
-extern "C" void printChar(const char*, bool errStream);
+/*extern "C" */void printChar(const char*, bool errStream);
 
 #ifndef UT699