fix bugrep 17257 build.sh install problem under cygwin

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@274468 13f79535-47bb-0310-9956-ffa450edef68

build.sh

@@ -54,6 +54,9 @@ export CLASSPATH
 
 
 if [ "$REALANTHOME" != "" ] ; then
+  if $cygwin; then
+     REALANTHOME=`cygpath --path --windows "$REALANTHOME"`
+  fi
   ANT_INSTALL="-Dant.install=$REALANTHOME"
 else
   ANT_INSTALL="-emacs"