[7u4] Request for approval for CR : 2221126: incorrect path separator in make/build.xml for Windows when running jtreg tests

[Jim Holmlund]

Request for Backport of a JDK 8 fix into 7u4.

This fixes a problem in the langtools/make/build.xml file that causes a problem for the jtreg 
targets on windows.

Bug description
    http://monaco.us.oracle.com/detail.jsf?cr=2221126

The fix is a one line change that is the same as in JDK 8:
JDK 8 changeset
    http://hg.openjdk.java.net/jdk8/tl/langtools/rev/cd5ca700da4c


jjh