arm64: use L() in the handful of places we didn't already.

Change-Id: Ieb3cc5c9623291421c1d2fdc204e27812fee8ffd
diff --git a/libc/arch-arm64/string/__memcpy_chk.S b/libc/arch-arm64/string/__memcpy_chk.S
index a8e9e83..c9fc2f7 100644
--- a/libc/arch-arm64/string/__memcpy_chk.S
+++ b/libc/arch-arm64/string/__memcpy_chk.S
@@ -31,10 +31,10 @@
 ENTRY(__memcpy_chk)
   cmp x2, x3
   // Direct b.ls memcpy may not have enough range
-  b.hi .L_memcpy_chk_fail
+  b.hi L(__memcpy_chk_fail_trampoline)
   b memcpy
 
-.L_memcpy_chk_fail:
+L(__memcpy_chk_fail_trampoline):
   // Preserve for accurate backtrace.
   stp x29, x30, [sp, -16]!
   .cfi_def_cfa_offset 16