it seems that my problem was not related to sources jar availability.
Building monolitic jars doesn't help.
I was suspecting that 2.8-SNAPSHOT compiler fails because it misses sources, but now I'm not sure.
[INFO] Found 0 cached/archived units. Used 0 / 4446 units from cache.
[INFO] Compiling...
[INFO] 0% complete (ETR: 53 seconds)
[INFO] 10% complete (ETR: 50 seconds)
[INFO] 20% complete (ETR: 31 seconds)
[INFO] 30% complete (ETR: 29 seconds)
[INFO] 40% complete (ETR: 22 seconds)
[INFO] 50% complete (ETR: 17 seconds)
[INFO] 60% complete (ETR: 14 seconds)
[INFO] 70% complete (ETR: 11 seconds)
[INFO] 80% complete (ETR: 7 seconds)
[INFO] 90% complete (ETR: 3 seconds)
[INFO] 100% complete (ETR: 0 seconds)
[INFO] Compilation completed in 36.48 seconds
[INFO] [ERROR] Unexpected internal compiler error
[INFO] java.lang.IllegalArgumentException
[INFO] at org.objectweb.asm.ClassReader.<init>(Unknown Source)
[INFO] at org.objectweb.asm.ClassReader.<init>(Unknown Source)
[INFO] at com.google.gwt.dev.javac.BytecodeSignatureMaker.visitCompileDependenciesInBytecode(BytecodeSignatureMaker.java:226)
[INFO] at com.google.gwt.dev.javac.BytecodeSignatureMaker.getCompileDependencySignature(BytecodeSignatureMaker.java:209)
[INFO] at com.google.gwt.dev.javac.CompiledClass.getSignatureHash(CompiledClass.java:165)
[INFO] at com.google.gwt.dev.javac.Dependencies$Ref.<init>(Dependencies.java:41)
[INFO] at com.google.gwt.dev.javac.Dependencies$Ref.<init>(Dependencies.java:36)
[INFO] at com.google.gwt.dev.javac.Dependencies.resolve(Dependencies.java:100)
[INFO] at com.google.gwt.dev.javac.CompilationStateBuilder$CompileMoreLater.compile(CompilationStateBuilder.java:352)
[INFO] at com.google.gwt.dev.javac.CompilationStateBuilder.doBuildFrom(CompilationStateBuilder.java:548)
[INFO] at com.google.gwt.dev.javac.CompilationStateBuilder.buildFrom(CompilationStateBuilder.java:479)
[INFO] at com.google.gwt.dev.javac.CompilationStateBuilder.buildFrom(CompilationStateBuilder.java:465)
[INFO] at com.google.gwt.dev.cfg.ModuleDef.getCompilationState(ModuleDef.java:423)
[INFO] at com.google.gwt.dev.Precompile.precompile(Precompile.java:222)
[INFO] at com.google.gwt.dev.Precompile.precompile(Precompile.java:202)
[INFO] at com.google.gwt.dev.Precompile.precompile(Precompile.java:143)
[INFO] at com.google.gwt.dev.Compiler.run(Compiler.java:197)
[INFO] at com.google.gwt.dev.Compiler.run(Compiler.java:156)
[INFO] at com.google.gwt.dev.Compiler$1.run(Compiler.java:117)
[INFO] at com.google.gwt.dev.CompileTaskRunner.doRun(CompileTaskRunner.java:55)
[INFO] at com.google.gwt.dev.CompileTaskRunner.runWithAppropriateLogger(CompileTaskRunner.java:50)
[INFO] at com.google.gwt.dev.Compiler.main(Compiler.java:124)
The only asm version in classpath is 5.0.3.