Disable exit-on-SIGPIPE in lldb

Occasionally, during test teardown, LLDB writes to a closed pipe.
Sometimes the communication is inherently unreliable, so LLDB tries to
avoid being killed due to SIGPIPE (it calls `signal(SIGPIPE, SIG_IGN)`).
However, LLVM's default SIGPIPE behavior overrides LLDB's, causing it to
exit with IO_ERR.

Opt LLDB out of the default SIGPIPE behavior. I expect that this will
resolve some LLDB test suite flakiness (tests randomly failing with
IO_ERR) that we've seen since r344372.

rdar://55750240

Differential Revision: https://reviews.llvm.org/D69148

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@375288 91177308-0d34-0410-b5e6-96231b3b80d8

Author: vedantk

tools/driver/Driver.cpp

@@ -853,6 +853,16 @@ int main(int argc, char const *argv[])
   signal(SIGCONT, sigcont_handler);
 #endif
 
+  // Occasionally, during test teardown, LLDB writes to a closed pipe.
+  // Sometimes the communication is inherently unreliable, so LLDB tries to
+  // avoid being killed due to SIGPIPE. However, LLVM's default SIGPIPE behavior
+  // is to exit with IO_ERR. Opt LLDB out of that.
+  //
+  // We don't disable LLVM's signal handling entirely because we still want
+  // pretty stack traces, and file cleanup (for when, say, the clang embedded
+  // in LLDB leaves behind temporary objects).
+  llvm::sys::SetPipeSignalFunction(nullptr);
+
   int exit_code = 0;
   // Create a scope for driver so that the driver object will destroy itself
   // before SBDebugger::Terminate() is called.