It turns out that the "-nostdlib" switch that we've been using

has been unncessary for quite a long time.  It turns out that if
we don't call and stdlib functions, then no stdlib bloat gets
added (duh.)  Thanks to matthijskooijman for finally noticing this.
It fixes bugs related to using the EEPROM functions (from stdlib)
in spite of library name changes between compiler versions.
(Now compiles with gcc 3.4.x though gcc 5.2.x, AFAICT.)
https://github.com/Optiboot/optiboot/issues/233
https://github.com/Optiboot/optiboot/issues/177

optiboot/bootloaders/optiboot/Makefile

@@ -126,19 +126,12 @@ OPTIMIZE = -Os -fno-split-wide-types -mrelax
 
 DEFS       = 
 
-#
-# platforms support EEPROM and large bootloaders need the eeprom functions that
-# are defined in libc, even though we explicity remove it with -nostdlib because
-# of the space-savings.
-LIBS       =  -lc
-
 CC         = $(GCCROOT)avr-gcc
 
 # Override is only needed by avr-lib build system.
 
 override CFLAGS        = -g -Wall $(OPTIMIZE) -mmcu=$(MCU_TARGET) -DF_CPU=$(AVR_FREQ) $(DEFS)
-override LDFLAGS       = $(LDSECTIONS) -Wl,--relax -nostartfiles -nostdlib
-#-Wl,--gc-sections
+override LDFLAGS       = $(LDSECTIONS) -Wl,--relax -nostartfiles
 
 OBJCOPY        = $(GCCROOT)avr-objcopy
 OBJDUMP        = $(call fixpath,$(GCCROOT)avr-objdump)