Move ElfLoader from libart-compiler-llvm to libart.

Due to the fact that we are going to use ElfLoader
in OatFile, CommonTest, and Compiler, it won't be a
good idea to keep ElfLoader as backend specific class.
Thus, we should move ElfLoader to libart.

Change-Id: I3d264266b3771eaa935b1768be1937797f57f7d7
diff --git a/build/Android.common.mk b/build/Android.common.mk
index 8191b43..b2a983e 100644
--- a/build/Android.common.mk
+++ b/build/Android.common.mk
@@ -187,6 +187,7 @@
 
 ifeq ($(ART_USE_LLVM_COMPILER),true)
 LIBART_COMMON_SRC_FILES += \
+	src/compiler_llvm/elf_loader.cc \
 	src/compiler_llvm/inferred_reg_category_map.cc \
 	src/compiler_llvm/runtime_support_llvm.cc \
 	src/compiler_llvm/utils_llvm.cc