[wip/sysdep/pal-distro.mk] Change CMAKE_PATH only if the user ask for it.

sysdep/pal-distro.mk

@@ -6,12 +6,13 @@ ifndef _paldistro_mk
   _paldistro:=$(shell ${SHELL} ${ROBOTPKG_DIR}/wip/sysdep/pal-distro.sh)
   export PALDISTRO:=  $(word 1,${_paldistro})
 
-  ifeq (palerbium,${PALDISTRO})
-     ifeq (yes,$(call exists,${ROBOTPKG_DIR}/wip/sysdep/platform/${PALDISTRO}.mk))
-	include ${ROBOTPKG_DIR}/wip/sysdep/platform/${PALDISTRO}.mk
-     else
-        $(error missing wip/sysdep/platform/${PALDISTRO}.mk)
+  ifeq (erbium,${PREFER.pal-distro})	
+     ifeq (palerbium,${PALDISTRO})
+        ifeq (yes,$(call exists,${ROBOTPKG_DIR}/wip/sysdep/platform/${PALDISTRO}.mk))
+	   include ${ROBOTPKG_DIR}/wip/sysdep/platform/${PALDISTRO}.mk
+        else
+           $(error missing wip/sysdep/platform/${PALDISTRO}.mk)
+        endif
      endif
   endif
-
 endif # ERBIUM_ROS_FLAVOR