kbuild: Made cmd_link_multi readable

Introduced ld_flags, and separated out the common parts of link_multi
for normal and module objects.
Added a bit of a comment as well

scripts/Makefile.build

@@ -236,11 +236,20 @@ endif
 #
 # Rule to link composite objects
 #
+#  Composite objects are specified in kbuild makefile as follows:
+#    <composite-object>-objs := <list of .o files>
+#  or
+#    <composite-object>-y    := <list of .o files>
+link_multi_deps =                     \
+$(filter $(addprefix $(obj)/,         \
+$($(subst $(obj)/,,$(@:.o=-objs)))    \
+$($(subst $(obj)/,,$(@:.o=-y)))), $^)
+ 
 quiet_cmd_link_multi-y = LD      $@
-cmd_link_multi-y = $(LD) $(LDFLAGS) $(EXTRA_LDFLAGS) -r -o $@ $(filter $(addprefix $(obj)/,$($(subst $(obj)/,,$(@:.o=-objs))) $($(subst $(obj)/,,$(@:.o=-y)))),$^)
+cmd_link_multi-y = $(LD) $(ld_flags) -r -o $@ $(link_multi_deps)
 
 quiet_cmd_link_multi-m = LD [M]  $@
-cmd_link_multi-m = $(LD) $(LDFLAGS) $(EXTRA_LDFLAGS) $(LDFLAGS_MODULE) -o $@ $(filter $(addprefix $(obj)/,$($(subst $(obj)/,,$(@:.o=-objs))) $($(subst $(obj)/,,$(@:.o=-y)))),$^)
+cmd_link_multi-m = $(LD) $(ld_flags) $(LDFLAGS_MODULE) -o $@ $(link_multi_deps)
 
 # We would rather have a list of rules like
 # 	foo.o: $(foo-objs)

scripts/Makefile.lib

@@ -128,6 +128,7 @@ hostc_flags    = -Wp,-MD,$(depfile) $(HOSTCFLAGS) $(HOST_EXTRACFLAGS)\
 		 $(HOSTCFLAGS_$(*F).o)
 hostcxx_flags  = -Wp,-MD,$(depfile) $(HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS)\
 		 $(HOSTCXXFLAGS_$(*F).o)
+ld_flags       = $(LDFLAGS) $(EXTRA_LDFLAGS)
 
 # Finds the multi-part object the current object will be linked into
 modname-multi = $(sort $(foreach m,$(multi-used),\