Ignore SIGPIPE in the bssl tool.

Bug: 435
Change-Id: I0ed94d40d04ebc26c9996dfe2b947a6e2f140a89
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/49465
Reviewed-by: Adam Langley <agl@google.com>

tool/tool.cc

@@ -24,6 +24,7 @@
 #include <io.h>
 #else
 #include <libgen.h>
+#include <signal.h>
 #endif
 
 #include "internal.h"
@@ -106,6 +107,8 @@ int main(int argc, char **argv) {
     perror("_setmode(_fileno(stderr), O_BINARY)");
     return 1;
   }
+#else
+  signal(SIGPIPE, SIG_IGN);
 #endif
 
   CRYPTO_library_init();