Add -DSIGNAL_PROVIDED to nacl build.

newlib/configure.host

 # configure.host
 
 # This shell script handles all host based configuration for newlib.
 # It sets various shell variables based on the the host and the
 # configuration options.  You can modify this shell script without
 # needing to rerun autoconf.
 
 # This shell script should be invoked as
 #   . configure.host
 # If it encounters an error, it will exit with a message.
@@ skipping 333 matching lines @@
 # including crt0.
 # THIS TABLE IS ALPHA SORTED.  KEEP IT THAT WAY.
 
 case "${host}" in
   *-*-cygwin*)
         posix_dir=posix
         stdio64_dir=stdio64
         xdr_dir=xdr
         ;;
   *-*-nacl*)
-        newlib_cflags="${newlib_cflags} -DCLOCK_PROVIDED -DHAVE_NANOSLEEP -DMALLOC_PROVIDED"
+        newlib_cflags="${newlib_cflags} -DSIGNAL_PROVIDED -DCLOCK_PROVIDED -DHAVE_NANOSLEEP -DMALLOC_PROVIDED"
         sys_dir=nacl
         posix_dir=posix
         ;;
   *-*-netware*)
         signal_dir=
         sys_dir=netware
         ;;
   *-*-rtems*)                   # generic RTEMS support
         sys_dir=rtems
         posix_dir=posix
@@ skipping 434 matching lines @@
 fi
 
 # Remove rpc headers if xdr_dir not specified
 if [ "x${xdir_dir}" = "x" ]; then
         noinclude="${noinclude} rpc/types.h rpc/xdr.h"
 fi
 
 if test -z "${have_crt0}" && test -n "${sys_dir}"; then
   have_crt0="yes"
 fi