biscuit: fix aarch64 toolchain prefix on linux

biscuit/CMakeLists.txt

@@ -27,7 +27,11 @@ elseif (${ARCH} STREQUAL riscv64)
     set(PREFIX              riscv64-unknown-elf-)
     set(CMAKE_C_FLAGS       "-march=rv64imac -mabi=lp64 -mcmodel=medany")
 elseif (${ARCH} STREQUAL aarch64)
+    if(APPLE)
         set(PREFIX          aarch64-none-elf-)
+    else()
+        set(PREFIX          aarch64-elf-)
+    endif ()
     set(LINK_FLAGS          "-Ttext 0xffff000000000000")
 else()
     message("Unsupported arch: ${ARCH}")