Android patch: Add '--small' option to makeconv call during .ucm to .cnv conversion

This change was introduced in Android by the ICU421 and ICU4.6 upgrades:

https://android.googlesource.com/platform/external/icu/+/85bf2e2
https://android.googlesource.com/platform/external/icu/+/27f6547

In ICU 64 build system has changed, migrating from Makefile to
python script when performing various data transformations, so that patch now
patches BUILDRULES.py and adds '--small' option there.

Test: n/a
Change-Id: If88d126d738c50ed91d55e7695fc133627eca575
1 file changed