[jitzygote] Remap boot boot image methods in zygote when single-threaded.

This avoids concurrent updates made by other threads while copying the
data.

Bug: 143569713
Bug: 119800099
Test: boots
Change-Id: Ife0141a45b8d8671ab0c5868ccf90b4799a9f5db
diff --git a/libartbase/base/utils.h b/libartbase/base/utils.h
index 6fc537a..4bcb915 100644
--- a/libartbase/base/utils.h
+++ b/libartbase/base/utils.h
@@ -159,6 +159,9 @@
 // following accesses repopulate the memory or return zero.
 bool IsAddressKnownBackedByFileOrShared(const void* addr);
 
+// Returns the number of threads running.
+int GetTaskCount();
+
 }  // namespace art
 
 #endif  // ART_LIBARTBASE_BASE_UTILS_H_