define WIN32_LEAN_AND_MEAN only while compiling gcc #225

Job	Run time
build (ubuntu-latest, clean, i386-pc-msdosdjgpp, binutils gcc djgpp-2.05 watt32)	13m 25s
build (ubuntu-latest, clean, i386-pc-msdosdjgpp, binutils gcc djgpp-cvs watt32)	13m 55s
build (ubuntu-latest, clean, i386-pc-msdosdjgpp, gdb)	4m 22s
build (ubuntu-latest, clean, arm-eabi, binutils gcc newlib)	25m 42s
build (ubuntu-latest, clean, arm-eabi, gdb)	6m 50s
build (ubuntu-latest, clean, avr, binutils gcc avr-libc)	43m 40s
build (ubuntu-latest, clean, avr, gdb avarice simulavr avrdude)	55s
build (ubuntu-latest, clean, ia16-elf, binutils gcc newlib)	6m 1s
build (macos-latest, clean, i386-pc-msdosdjgpp, binutils gcc djgpp-2.05 watt32)	45m 22s
build (macos-latest, clean, i386-pc-msdosdjgpp, binutils gcc djgpp-cvs watt32)	30m 14s
build (macos-latest, clean, i386-pc-msdosdjgpp, gdb)	3m 54s
build (macos-latest, clean, arm-eabi, binutils gcc newlib)	1h 1m 52s
build (macos-latest, clean, arm-eabi, gdb)	5m 45s
build (macos-latest, clean, avr, binutils gcc avr-libc)	2h 2m 23s
build (macos-latest, clean, avr, gdb avarice simulavr avrdude)	2m 43s
build (macos-latest, clean, ia16-elf, binutils gcc newlib)	12m 9s
	6h 39m 12s

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