icu build: use genccode -o on non-windows platforms

[srl295]

• Platform: all
• Subsystem: deps

some (all?) non-windows platforms we build on, could support ICU's .dat-to-.obj file conversion via assembler, but right now it's only enabled on windows. Others get:

generating C code for /Users/srl/src/node/out/Release/obj/gen/icudt62.dat
  CC(target) /Users/srl/src/node/out/Release/obj.target/icudata/gen/icudt62_dat.o

…and yes, that's a hefty .c file. i found/refound this when @bnoordhuis started re-implementing what ICU aready supports.

I think a small whitelist of compilers/platforms might suffice: gcc/linux, gcc/aix, gcc/mac, gcc/mingw, gcc/solaris ( Hmm, I guess that's just one compiler)

On windows, we use the -o option which outputs a .obj file directly with no intermediate files.

advantage would be to speed up the build a little bit, probably reduce max memory/swap footprint.

[richardlau]

@srl295 Was this part of #29522 (I seem to recall some discussion there about assemblers)?

[srl295]

@srl295 Was this part of #29522 (I seem to recall some discussion there about assemblers)?

Good catch! Yes, I did this in #29522