The wbapi tests do not run correctly on cygwin (they run correctly on mks, solaris and linux).
Sample test failure from jprt with -release jdk8 (which uses cygwin):

( C:/jprt/products/P1/gnumake3.81/cygwin/bin/make.exe ALT_SLASH_JAVA=C:/jprt/slashjava JPRT_PRODUCT_PATH=C:/jprt/temp/P1/211057.jcoomes/testproduct/windows_i586_5.1-fastdebug
  JPRT_ARCHIVE_BUNDLE=C:/jprt/temp/P1/211057.jcoomes/bundles/windows_i586-fastdebug-c1-wbapitest.zip wbapitest )
rm -f -r /cygdrive/c/jprt/temp/P1/211057.jcoomes/source/test/../build/-/testoutput
rm -f C:/jprt/temp/P1/211057.jcoomes/bundles/windows_i586-fastdebug-c1-wbapitest.zip
C:/jprt/products/P1/jtreg4.1-latest/jtreg/win32/bin/jtreg -a -v:fail,error \
          -k:\!ignore \
                          \
          -r:/cygdrive/c/jprt/temp/P1/211057.jcoomes/source/test/../build/-/testoutput/JTreport \
          -w:/cygdrive/c/jprt/temp/P1/211057.jcoomes/source/test/../build/-/testoutput/JTwork \
          -jdk:C:/jprt/temp/P1/211057.jcoomes/testproduct/windows_i586_5.1-fastdebug \
          -vmoption:-client -vmoption:-Duser.home=C:/jprt/temp/P1/211057.jcoomes -vmoption:-Djava.io.tmpdir=C:/jprt/temp/P1/211057.jcoomes/io/windows_i586-fastdebug-c1-wbapitest \
          /cygdrive/c/jprt/temp/P1/211057.jcoomes/source/test/sanity \
|| ( exitCode=$? && ( mkdir -p `dirname C:/jprt/temp/P1/211057.jcoomes/bundles/windows_i586-fastdebug-c1-wbapitest.zip` && cd /cygdrive/c/jprt/temp/P1/211057.jcoomes/source/test/../build/-/testoutput && zip -q -r
  C:/jprt/temp/P1/211057.jcoomes/bundles/windows_i586-fastdebug-c1-wbapitest.zip . ) && exit ${exitCode} )
Error: Cannot find file: \cygdrive\c\jprt\temp\P1\211057.jcoomes\source\test\sanity

zip error: Nothing to do! (try: zip -q -r C:/jprt/temp/P1/211057.jcoomes/bundles/windows_i586-fastdebug-c1-wbapitest.zip . -i .)
make: *** [wbapitest] Error 12