Compilation Fix to build.

This change is to fix the compilation.

Change-Id: Ic51e0c0687d566a323b4c4e02bc2c999d85ecd0f
diff --git a/libc/arch-arm/cortex-a53/cortex-a53.mk b/libc/arch-arm/cortex-a53/cortex-a53.mk
index 3ed80f2..f7f18b9 100644
--- a/libc/arch-arm/cortex-a53/cortex-a53.mk
+++ b/libc/arch-arm/cortex-a53/cortex-a53.mk
@@ -5,6 +5,7 @@
     arch-arm/cortex-a15/bionic/strcmp.S \
     arch-arm/cortex-a15/bionic/strcpy.S \
     arch-arm/cortex-a15/bionic/strlen.S \
+    arch-arm/cortex-a15/bionic/stpcpy.S \
     arch-arm/cortex-a15/bionic/__strcat_chk.S \
     arch-arm/cortex-a15/bionic/__strcpy_chk.S \
     arch-arm/krait/bionic/memmove.S