Ant task - "stdlib" attribute checked to be non-empty, empty default is specified in tests

build-tools/build.xml

@@ -77,7 +77,7 @@
         <attribute name="file"           default=""/>
         <attribute name="srcdir"         default=""/>
         <attribute name="includeRuntime" default="true"/>
-        <attribute name="stdlib"         default="${kotlin-home}/lib/kotlin-runtime.jar"/>
+        <attribute name="stdlib"         default=""/>
 
         <sequential>
 
@@ -102,7 +102,7 @@
         <attribute name="srcdir"         default=""/>
         <attribute name="module"         default=""/>
         <attribute name="includeRuntime" default="true"/>
-        <attribute name="stdlib"         default="${kotlin-home}/lib/kotlin-runtime.jar"/>
+        <attribute name="stdlib"         default=""/>
         <sequential>
 
             <cleanup/>

build-tools/core/src/org/jetbrains/jet/buildtools/core/BytecodeCompiler.java

@@ -13,7 +13,7 @@ public class BytecodeCompiler {
 
     public BytecodeCompiler ( String stdlib ) {
         ENV = new CompileEnvironment();
-        if ( stdlib != null ) {
+        if (( stdlib != null ) && ( stdlib.trim().length() > 0 )) {
             ENV.setStdlib( stdlib );
         }
     }