Simplify build script; support 'clean'

h2/build.bat

 @echo off
 if "%JAVA_HOME%"=="" echo Error: JAVA_HOME is not defined.
-if "%1"=="-Dclean" rmdir /s /q temp | rmdir /s /q bin
+if "%1"=="clean" rmdir /s /q temp | rmdir /s /q bin
 if not exist temp mkdir temp
 if not exist bin mkdir bin
-if exist bin/org/h2/build/Build.class goto buildOK
-javac -sourcepath src/tools -d bin src/tools/org/h2/build/*.java
-:buildOK
+javac -source 1.4 -sourcepath src/tools -d bin src/tools/org/h2/build/*.java
 "%JAVA_HOME%/bin/java" -Xmx256m -cp "bin;%JAVA_HOME%/lib/tools.jar;temp" org.h2.build.Build %*
\ No newline at end of file

h2/build.sh

@@ -6,16 +6,8 @@ if [ -z "$JAVA_HOME" ] ; then
     echo "Error: JAVA_HOME is not defined."
   fi
 fi
-if [ $1 == "-Dclean" ] ; then
-  rm -rf temp bin
-fi
-if [ ! -d "temp" ] ; then
-  mkdir temp
-fi
-if [ ! -d "bin" ] ; then
-  mkdir bin
-fi
-if [ ! -f "bin/org/h2/build/Build.class" ] ; then
-  javac -sourcepath src/tools -d bin src/tools/org/h2/build/*.java
-fi
+if [ $1 == "clean" ] ; then rm -rf temp bin ; fi
+if [ ! -d "temp" ] ; then mkdir temp ; fi
+if [ ! -d "bin" ] ; then mkdir bin ; fi
+javac -source 1.4 -sourcepath src/tools -d bin src/tools/org/h2/build/*.java
 "$JAVA_HOME/bin/java" -Xmx256m -cp "bin:$JAVA_HOME/lib/tools.jar:temp" org.h2.build.Build $@