OPENJDK variable is set after Platform.gmk is loaded.
It should be set before including other files (it is used in the Platform.gmk for freetype-related logic)
(In fact this is generic problem with easy woraround - just set environment variable prior to running make).

Cygwin build fails on compilation of generated java files with listing of locales.
It failed because string literals contained bunch of "\r" chars.
These were introduced by cygwin's awk.

Solution is to always explicitly request binary mode for awk.
It can be done either explicitly in the make\java\java\localegen.sh
($localelist=`$NAWK -v BINARY=w -F....)
or (better) "-v BINARY=w" should be added to NAWK definition
(btw, we do already distinguish cygwin case when define NAWK).
In later case additional changes in the makefiles will be required to properly
call awk.
E.g. in the make\java\java\genlocales.gmk instead of
NAWK=$(NAWK) SED=$(SED) $(SH) $(LOCALEGEN_SH) ...
use
NAWK="$(NAWK)" SED=$(SED) $(SH) $(LOCALEGEN_SH) ...

Things to fix in the README-builds.html:
  - introduce ALT_JDK_IMPORT_PATH
  - mention that cygwin make has to be downgraded to 3.80
  - may be introduce ALT_UNICOWS_* (unless it will be removed from the build requirements)
  - mention that following Cygwin packages are required: zip, unzip
  - perhaps insert sample bat file to be used to start build
     (for linux build sample shell script can be useful for begginers).