Unkillable build when script has syntax error

{/* supposed to be a block but this is wrong */}

ERROR: failed to start build
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
WorkflowScript: 2: Ambiguous expression could be either a parameterless closure expression or an isolated open code block;
   solution: Add an explicit closure parameter list, e.g. {it -> ...}, or force it to be treated as an open block by giving it a label, e.g. L:{...} @ line 2, column 1.
   {
   ^

1 error

	at org.codehaus.groovy.control.ErrorCollector.failIfErrors(ErrorCollector.java:302)
	at org.codehaus.groovy.control.ErrorCollector.addFatalError(ErrorCollector.java:149)
	at org.codehaus.groovy.control.ErrorCollector.addError(ErrorCollector.java:119)
	at org.codehaus.groovy.control.ErrorCollector.addError(ErrorCollector.java:131)
	at org.codehaus.groovy.control.SourceUnit.addError(SourceUnit.java:359)
	at org.codehaus.groovy.antlr.AntlrParserPlugin.transformCSTIntoAST(AntlrParserPlugin.java:142)
	at org.codehaus.groovy.antlr.AntlrParserPlugin.parseCST(AntlrParserPlugin.java:108)
	at org.codehaus.groovy.control.SourceUnit.parse(SourceUnit.java:236)
	at org.codehaus.groovy.control.CompilationUnit$1.call(CompilationUnit.java:161)
	at org.codehaus.groovy.control.CompilationUnit.applyToSourceUnits(CompilationUnit.java:846)
	at org.codehaus.groovy.control.CompilationUnit.doPhaseOperation(CompilationUnit.java:550)
	at org.codehaus.groovy.control.CompilationUnit.processPhaseOperations(CompilationUnit.java:526)
	at org.codehaus.groovy.control.CompilationUnit.compile(CompilationUnit.java:503)
	at groovy.lang.GroovyClassLoader.doParseClass(GroovyClassLoader.java:302)
	at groovy.lang.GroovyClassLoader.parseClass(GroovyClassLoader.java:281)
	at groovy.lang.GroovyShell.parseClass(GroovyShell.java:731)
	at groovy.lang.GroovyShell.parse(GroovyShell.java:743)
	at org.jenkinsci.plugins.workflow.cps.CpsGroovyShell.reparse(CpsGroovyShell.java:100)
	at org.jenkinsci.plugins.workflow.cps.CpsFlowExecution.parseScript(CpsFlowExecution.java:346)
	at org.jenkinsci.plugins.workflow.cps.CpsFlowExecution.start(CpsFlowExecution.java:314)
	at org.jenkinsci.plugins.workflow.job.WorkflowRun.run(WorkflowRun.java:176)
	at hudson.model.ResourceController.execute(ResourceController.java:89)
	at hudson.model.Executor.run(Executor.java:240)
	at hudson.model.OneOffExecutor.run(OneOffExecutor.java:43)