Use linker "--relax" option.

The "relax" option enables the linker to convert certain "call"
instructions to the smaller "rcall" instruction.  This reduces the
size of the resulting binary.

Marlin/Makefile

@@ -254,7 +254,7 @@ endif
 CFLAGS = $(CDEBUG) $(CDEFS) $(CINCS) -O$(OPT) $(CWARN) $(CEXTRA) $(CTUNING)
 CXXFLAGS =         $(CDEFS) $(CINCS) -O$(OPT) -Wall    $(CEXTRA) $(CTUNING)
 #ASFLAGS = -Wa,-adhlns=$(<:.S=.lst),-gstabs 
-LDFLAGS = -lm
+LDFLAGS = -lm -Wl,--relax
 
 
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