Re-enable tests with the optimizing compiler.

Tests run ok on my host/target. I reverted the move to
using thumb2, because tests were crashing. But I could not
reproduce file limits issues.

Make SignalTest as crashing for optimizing. We need to implement
stack overflow checks.

Change-Id: Ieda575501eaf30af7aaa2c44e71544c9c467c24f
diff --git a/compiler/optimizing/optimizing_compiler.cc b/compiler/optimizing/optimizing_compiler.cc
index 56029aa..ccacbef 100644
--- a/compiler/optimizing/optimizing_compiler.cc
+++ b/compiler/optimizing/optimizing_compiler.cc
@@ -101,6 +101,10 @@
   }
 
   InstructionSet instruction_set = GetCompilerDriver()->GetInstructionSet();
+  // The optimizing compiler currently does not have a Thumb2 assembler.
+  if (instruction_set == kThumb2) {
+    instruction_set = kArm;
+  }
   CodeGenerator* codegen = CodeGenerator::Create(&arena, graph, instruction_set);
   if (codegen == nullptr) {
     if (shouldCompile) {