Fix nasa#710, allow setting of processor ID in targets.cmake

Add support for a TGTx_PROCESSOR_ID directive, which allows
one to set the default value returned by CFE_PSP_GetProcessorId()
function, rather than assuming the index value from CMake.

cmake/target/CMakeLists.txt

@@ -48,7 +48,11 @@ include_directories(${CMAKE_BINARY_DIR}/${CFE_CORE_TARGET}/inc)
 
 # The CPU ID and name are defined by the build scripts for this target
 if (DEFINED TGTID)
-  add_definitions(-DCFE_CPU_ID_VALUE=${TGTID})
+  if (DEFINED TGT${TGTID}_PROCESSORID)
+      add_definitions(-DCFE_CPU_ID_VALUE=${TGT${TGTID}_PROCESSORID})
+  else()
+      add_definitions(-DCFE_CPU_ID_VALUE=${TGTID})
+  endif()
 endif()
 if (DEFINED SPACECRAFT_ID)
   add_definitions(-DCFE_SPACECRAFT_ID_VALUE=${SPACECRAFT_ID})