Because of this issue it is not possible to bootstrap jdk9 any more with boot jdk prior to 8u40 (see error below).

We can either require a boot jdk which is 8u40 or higher or fix this error which is not too hard.

Compiling 1027 files for BUILD_INTERIM_LANGTOOLS
( /cygdrive/c/output/OpenJDK/output-jdk9-dev-opt/configure-support/bin/fixpath.exe -c /cygdrive/c/Software/Java/jdk1.8.0_20/bin/javac -XDignore.symbol.file=true -g -Xlint:all,-deprecation -Werror -g -implicit:none -d /cygdrive/c/output/OpenJDK/output-jdk9-dev-opt/buildtools/langtools_interim_classes @/cygdrive/c/output/OpenJDK/output-jdk9-dev-opt/buildtools/langtools_interim_classes/_the.BUILD_INTERIM_LANGTOOLS_batch.tmp > >(/usr/bin/tee /cygdrive/c/output/OpenJDK/output-jdk9-dev-opt/buildtools/langtools_interim_classes/_the.BUILD_INTERIM_LANGTOOLS_batch.log) 2> >(/usr/bin/tee /cygdrive/c/output/OpenJDK/output-jdk9-dev-opt/buildtools/langtools_interim_classes/_the.BUILD_INTERIM_LANGTOOLS_batch.log >&2) || ( exitcode=$? && /usr/bin/cp /cygdrive/c/output/OpenJDK/output-jdk9-dev-opt/buildtools/langtools_interim_classes/_the.BUILD_INTERIM_LANGTOOLS_batch.log /cygdrive/c/output/OpenJDK/output-jdk9-dev-opt/make-support/failure-logs/buildtools_langtools_interim_classes__the.BUILD_INTERIM_LANGTOOLS_batch.log && exit $exitcode )
) && /usr/bin/mv /cygdrive/c/output/OpenJDK/output-jdk9-dev-opt/buildtools/langtools_interim_classes/_the.BUILD_INTERIM_LANGTOOLS_batch.tmp /cygdrive/c/output/OpenJDK/output-jdk9-dev-opt/buildtools/langtools_interim_classes/_the.BUILD_INTERIM_LANGTOOLS_batch
c:\Software\OpenJDK\jdk9-dev\langtools\src\jdk.javadoc\share\classes\jdk\javadoc\internal\doclets\toolkit\util\Utils.java:179: error: no suitable method found for collect(Collector<Object,CAP#1,ArrayList<Object>>)
                .collect(Collectors.toCollection(ArrayList::new));
                ^
    method Stream.<R#1>collect(Supplier<R#1>,BiConsumer<R#1,? super CAP#2>,BiConsumer<R#1,R#1>) is not applicable
      (cannot infer type-variable(s) R#1
        (actual and formal argument lists differ in length))
    method Stream.<R#2,A>collect(Collector<? super CAP#2,A,R#2>) is not applicable
      (cannot infer type-variable(s) R#2,A,CAP#3,T#2,C,E
        (argument mismatch; Collector<CAP#2,CAP#4,ArrayList<CAP#2>> cannot be converted to Collector<? super CAP#2,CAP#4,ArrayList<CAP#2>>))
  where R#1,T#1,R#2,A,T#2,C,E are type-variables:
    R#1 extends Object declared in method <R#1>collect(Supplier<R#1>,BiConsumer<R#1,? super T#1>,BiConsumer<R#1,R#1>)
    T#1 extends Object declared in interface Stream
    R#2 extends Object declared in method <R#2,A>collect(Collector<? super T#1,A,R#2>)
    A extends Object declared in method <R#2,A>collect(Collector<? super T#1,A,R#2>)
    T#2 extends Object declared in method <T#2,C>toCollection(Supplier<C>)
    C extends Collection<T#2> declared in method <T#2,C>toCollection(Supplier<C>)
    E extends Object declared in class ArrayList
  where CAP#1,CAP#2,CAP#3,CAP#4 are fresh type-variables:
    CAP#1 extends Object from capture of ?
    CAP#2 extends Element from capture of ? extends Element
    CAP#3 extends Object from capture of ?
    CAP#4 extends Object from capture of ?