From https://github.com/crystax/android-toolchain-gcc-5/commit/1e57465b9b81699ce8eb603dd4794a839a74c635

diff -u -r ../gcc-5.3.0/gcc/config/aarch64/aarch64-linux.h ./gcc/config/aarch64/aarch64-linux.h
--- ../gcc-5.3.0/gcc/config/aarch64/aarch64-linux.h	2015-07-24 12:00:26.000000000 -0400
+++ ./gcc/config/aarch64/aarch64-linux.h	2016-03-19 21:35:07.467502590 -0400
@@ -23,6 +23,12 @@
 
 #define GLIBC_DYNAMIC_LINKER "/lib/ld-linux-aarch64%{mbig-endian:_be}%{mabi=ilp32:_ilp32}.so.1"
 
+/* Use /sysystem/bin/linker64 as linker instead of 32-bit /system/bin/linker */
+#ifdef BIONIC_DYNAMIC_LINKER
+# undef BIONIC_DYNAMIC_LINKER
+#endif
+#define BIONIC_DYNAMIC_LINKER "/system/bin/linker64"
+
 #undef  ASAN_CC1_SPEC
 #define ASAN_CC1_SPEC "%{%:sanitize(address):-funwind-tables}"