Speedup canned small-icu build

[srl295]

Checklist

• make -j4 test (UNIX) and
• vcbuild test nosign (Windows) passes
• test on big endian
• a test and/or benchmark is included
• documentation is changed or added
• the commit message follows commit guidelines

Affected core subsystem(s)

Description of change

When:

• using canned, small-icu (the default for configure && make)
• .. on little endian systems

we can avoid building some things we're currently building.

Namely, on the host toolchain side in this scenario, only genccode needs to be compiled,
and it doesn't need the i18n or io libraries

Fixes: #7253

[srl295]

Started a CI build.

i18n.cc:(.text._ZN2v88internal12_GLOBAL__N_117CreateICUCollatorEPNS0_7IsolateERKN6icu_576LocaleENS0_6HandleINS0_8JSObjectEEE+0x2c): undefined reference to `icu_57::Collator::createInstance(icu_57::Locale const&, UErrorCode&)'
collect2: error: ld returned 1 exit status
make[1]: *** [/home/iojs/build/workspace/node-cross-compile/label/cc-armv6/out/Release/mksnapshot] Error 1

^ May need to re-include some stuff when cross-compiling.

[jasnell]

@srl295 ... what's the status on this?

[jasnell]

ping @srl295 ... does this need to stay open?

[srl295]

Probably not. I think enough has changed.

[fhinkel]

Ok, thanks @srl295 . Closing this.

[refack]

Cross-Ref: #12218
@srl295 is the icutrim.py patch an import from a different repo?

[srl295]

@refackicutrim.py is in a branch in ICU. but I have never landed it there.