Add -Xcheck:jni.

I think this is as complete as possible right now. The remaining
two #if 0 sections require:

1. a way to get the Method* of the current native method.
2. a way to get the Class* of the type of a given Field*.

Change-Id: I331586022095fb36ccc10c9ac1890a59a9224d01
diff --git a/build/Android.common.mk b/build/Android.common.mk
index a801889..bd8a83b 100644
--- a/build/Android.common.mk
+++ b/build/Android.common.mk
@@ -41,6 +41,7 @@
 LIBART_COMMON_SRC_FILES := \
 	src/assembler.cc \
 	src/calling_convention.cc \
+	src/check_jni.cc \
 	src/class_linker.cc \
 	src/compiler.cc \
 	src/compiler/Dataflow.cc \