removed obsolete THIS_IS_ISABELLE_BUILD feature: change environment after getsettings (works due to static scoping);

--- a/build	Thu Mar 06 19:21:20 2008 +0100
+++ b/build	Thu Mar 06 19:21:22 2008 +0100
@@ -18,13 +18,14 @@
 
 ## settings
 
-export THIS_IS_ISABELLE_BUILD=true
-
 PRG="$(basename "$0")"
 
 ISABELLE_HOME="$(cd "$(dirname "$0")"; pwd -P)"
 source "$ISABELLE_HOME/lib/scripts/getsettings" || exit 2
 
+ISABELLE_OUTPUT="$ISABELLE_HOME/heaps/$ML_IDENTIFIER"
+ISABELLE_BROWSER_INFO="$ISABELLE_HOME/browser_info"
+
 
 ## diagnostics