Fails on AIX: gmake releaseDist

Steps to reproduce, with a ''CFARM'' user account with the ksh login shell and no `.profile` or other such dotfile in its home directory:

The problem seems to be that `runConfigureICU` sets `INSTALL` in `icudefs.mk` to a bad value, to a relative path that doesn't resolve when being called from `stubdata/Makefile`.

A possible workaround is to manually pass a usable value for `INSTALL` to `runConfigureICU`:

Then the build works as expected.