Add optimized memchr implementation from newlib

Add NEON optimized memchr adapted from newlib

Change-Id: I91b2fafa243e4ab35fa56bb6171d48433c947cfd
Signed-off-by: Bernhard Rosenkränzer <Bernhard.Rosenkranzer@linaro.org>
diff --git a/libc/arch-arm64/generic-neon/generic-neon.mk b/libc/arch-arm64/generic-neon/generic-neon.mk
index f3bde5c..77e3861 100644
--- a/libc/arch-arm64/generic-neon/generic-neon.mk
+++ b/libc/arch-arm64/generic-neon/generic-neon.mk
@@ -1,4 +1,5 @@
 libc_bionic_src_files_arm64 += \
+    arch-arm64/generic/bionic/memchr.S \
     arch-arm64/generic/bionic/memcmp.S \
     arch-arm64/generic/bionic/memmove.S \
     arch-arm64/generic/bionic/memset.S \