Refactor jit debugger interface and its ELF creation.

Make it possible to store more then one method per entry,
and ref-count the number of live methods per entry.

Test: m test-art-host-gtest
Change-Id: I45d69185e85e47fbee88a8d1f549ede9875a3c0a
diff --git a/compiler/jit/jit_compiler.cc b/compiler/jit/jit_compiler.cc
index 88e3e5b..2c62095 100644
--- a/compiler/jit/jit_compiler.cc
+++ b/compiler/jit/jit_compiler.cc
@@ -76,6 +76,7 @@
     const ArrayRef<mirror::Class*> types_array(types, count);
     std::vector<uint8_t> elf_file = debug::WriteDebugElfFileForClasses(
         kRuntimeISA, jit_compiler->GetCompilerDriver()->GetInstructionSetFeatures(), types_array);
+    MutexLock mu(Thread::Current(), g_jit_debug_mutex);
     CreateJITCodeEntry(std::move(elf_file));
   }
 }