Revert "Add an error message to the default SIGPIPE handler"

It broke a PPC bot, for not immediately obvious reasons.

llvm/lib/Support/Unix/Signals.inc

@@ -432,10 +432,6 @@ void llvm::sys::SetOneShotPipeSignalFunction(void (*Handler)()) {
 }
 
 void llvm::sys::DefaultOneShotPipeSignalHandler() {
-  // UNIX03 conformance requires a non-zero exit code and an error message
-  // to stderr when writing to a closed stdout fails.
-  errs() << "error: write on a pipe with no reader\n";
-
   // Send a special return code that drivers can check for, from sysexits.h.
   exit(EX_IOERR);
 }

llvm/test/tools/llvm-nm/unix03-sigpipe-exit.test

@@ -1,17 +0,0 @@
-# Test that when nm tries to write to a closed stdout it will finish with
-# a non-zero exit code and an error message on stderr.
-# This is required for UNIX03 conformance.
-
-# UNSUPPORTED: system-windows
-
-# RUN: not %python %s llvm-nm llvm-nm 2>&1 | FileCheck %s
-# CHECK: error: write on a pipe with no reader
-
-import subprocess
-import sys
-
-with subprocess.Popen([sys.argv[1], sys.argv[2]], stdout=subprocess.PIPE) as process:
-  # Read single byte and immediately close pipe to trigger SIGPIPE.
-  process.stdout.read(1)
-  process.stdout.close()
-sys.exit(process.returncode)