Switch to NetBSD's strxfrm(3).

There were two bugs in our implementation. Intel found one, but another
remainined, and tracking upstream is the way forward for functions where
we add no value.

Change-Id: Ida9bac0293fb2c4cbc942b1e0515ee0477c6538b
diff --git a/libc/Android.mk b/libc/Android.mk
index fd81d7e..091b066 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -209,7 +209,6 @@
 	string/strstr.c \
 	string/strtok.c \
 	string/strtotimeval.c \
-	string/strxfrm.c \
 	string/__memcpy_chk.c \
 	string/__memmove_chk.c \
 	string/__memset_chk.c \
@@ -337,6 +336,7 @@
 	regex/regerror.c \
 	regex/regexec.c \
 	regex/regfree.c \
+	upstream-netbsd/libc/string/strxfrm.c \
 
 # The following files are common, but must be compiled
 # with different C flags when building a static C library.
@@ -467,6 +467,9 @@
     -DLOG_ON_HEAP_ERROR \
     -std=gnu99
 
+libc_common_cflags += \
+    -include upstream-netbsd/netbsd-compat.h
+
 # these macro definitions are required to implement the
 # 'timezone' and 'daylight' global variables, as well as
 # properly update the 'tm_gmtoff' field in 'struct tm'.