Allow opening a named pipe on MacOS and Linux.

runtime/bin/file_macos.cc

Index: runtime/bin/file_macos.cc
diff --git a/runtime/bin/file_macos.cc b/runtime/bin/file_macos.cc
index 81412f66e0c4440a4898e8bf8076cfae33fe7fcd..1b5ee0412284013032a881846c5478701cf65906 100644
--- a/runtime/bin/file_macos.cc
+++ b/runtime/bin/file_macos.cc
@@ -158,8 +158,8 @@ File* File::ScopedOpen(const char* name, FileOpenMode mode) {
   // Report errors for non-regular files.
   struct stat st;
   if (NO_RETRY_EXPECTED(stat(name, &st)) == 0) {
-    // Only accept regular files and character devices.
-    if (!S_ISREG(st.st_mode) && !S_ISCHR(st.st_mode)) {
+    // Only accept regular files, character devices, and pipes.
+    if (!S_ISREG(st.st_mode) && !S_ISCHR(st.st_mode) && !S_ISFIFO(st.st_mode)) {
       errno = (S_ISDIR(st.st_mode)) ? EISDIR : ENOENT;
       return NULL;
     }