just use 'which' and be done with it. the script was rather arcane, and
worked around deficiencies of cygwin (no longer relevant) and solaris
(assumed to be somewhat sane meanwhile).

Change-Id: I2e11ea3c87ac06a85604ac8d58d8fee95eae2e15
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>