Drop use of non-existing variable in KernelAddon rule.

* TARGET_KERNEL_PIC_FLAGS was probably meant to be 
  TARGET_KERNEL_PIC_CCFLAGS at the time this had been added in 2005.
  As correcting the name would mean that kernel add-ons would be 
  compiled such that they wouldn't be position independent, dropping
  the variable makes more sense (which is just a cleanup and doesn't 
  change anything due to that variable being always empty)

build/jam/KernelRules

@@ -134,7 +134,7 @@ rule KernelAddon
 	Depends $(target) : $(beginGlue) $(endGlue) ;
 
 	# compile and link
-	SetupKernel $(sources) : $(TARGET_KERNEL_PIC_FLAGS) : false ;
+	SetupKernel $(sources) : : false ;
 	local linkFlags = -nostdlib -Xlinker --no-undefined
 		-Xlinker -soname=\"$(target:G=)\" $(TARGET_KERNEL_ADDON_LINKFLAGS) ;
 	LINKFLAGS on $(target) = [ on $(target) return $(LINKFLAGS) ] $(linkFlags) ;