Revert "Enable gold linker for aarch64."

Causes build failures on Darwin.

prebuilts/gcc/darwin-x86/aarch64/aarch64-linux-android-4.9/aarch64-linux-android/bin/ld.gold: warning: cannot scan executable section 5 of out/target/product/flounder/obj/SHARED_LIBRARIES/libdl_intermediates/libdl.o for Cortex-A53 erratum because it has no mapping symbols.

prebuilts/gcc/darwin-x86/aarch64/aarch64-linux-android-4.9/aarch64-linux-android/bin/ld.gold: warning: cannot scan executable section 8 of out/target/product/flounder/obj/SHARED_LIBRARIES/libdl_intermediates/libdl.o for Cortex-A53 erratum because it has no mapping symbols.

prebuilts/gcc/darwin-x86/aarch64/aarch64-linux-android-4.9/aarch64-linux-android/bin/ld.gold: warning: cannot scan executable section 11 of out/target/product/flounder/obj/SHARED_LIBRARIES/libdl_intermediates/libdl.o for Cortex-A53 erratum because it has no mapping symbols.

prebuilts/gcc/darwin-x86/aarch64/aarch64-linux-android-4.9/aarch64-linux-android/bin/ld.gold: error: treating warnings as errors

This reverts commit 127d1101.

Change-Id: I1d3de90f5ae777b66a8f94fbcc9ccde8a9e3001c