Use PropagateContainerUpdateTargetFlags rule

Propagate all update variables in CopySetHaikuRevision and for the
kernel pseudo target.

build/jam/FileRules

@@ -341,8 +341,7 @@ rule CopySetHaikuRevision target : source
 		Depends $(target) : $(hgStore) ;
 	}
 
-	HAIKU_INCLUDE_IN_IMAGE on $(target)
-		= [ on $(source) return $(HAIKU_INCLUDE_IN_IMAGE) ] ;
+	PropagateContainerUpdateTargetFlags $(target) : $(source) ;
 
 	Depends $(target) : <build>copyattr <build>set_haiku_revision $(source) ;
 	CopySetHaikuRevision1 $(target)

src/system/kernel/Jamfile

@@ -170,9 +170,8 @@ Depends kernel : kernel_$(TARGET_ARCH) ;
 Depends kernel.so : kernel ;
 	# kernel.so will be rebuilt with the kernel
 
-# propagate HAIKU_INCLUDE_IN_IMAGE variable from kernel to kernel_$(TARGET_ARCH)
-HAIKU_INCLUDE_IN_IMAGE on kernel_$(TARGET_ARCH)
-		= [ on kernel return $(HAIKU_INCLUDE_IN_IMAGE) ] ;
+# propagate the container update variable from kernel to kernel_$(TARGET_ARCH)
+PropagateContainerUpdateTargetFlags kernel_$(TARGET_ARCH) : kernel ;
 
 # Copy kernel and update the copy's revision section. We link everything
 # against the original, but the copy will end up on the disk image (this way