RFR: JDK-8168607: langtools/test/Makefile should set -retain:fail,error by default

[Tim Bell]

Erik:

> This patch moves the langtools/test/Makefile one step closer being
> alignmened with the rest of the test/*/Makefiles by adding the
> -retain:fail,error jtreg option.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8168607
>
> Patch:
>
> diff -r ab39653a1e6d test/Makefile
> --- a/test/Makefile
> +++ b/test/Makefile
> @@ -161,6 +161,9 @@
>  JTREG_TESTVM_MEMORY_OPTION = -vmoption:-Xmx768m
>  JTREG_OPTIONS += $(JTREG_TESTVM_MEMORY_OPTION)
>
> +# Retain all files for failing tests
> +JTREG_OPTIONS += -retain:fail,error
> +
>  ifdef EXTRA_JTREG_OPTIONS
>    JTREG_OPTIONS += $(EXTRA_JTREG_OPTIONS)
>  endif

Thank you, Erik.  Looks good.

Tim