(_IO_new_file_fopen): Recognize 'e' flag and set O_CLOEXEC is needed.

this is a widely supported non-standard flag for fopen.

Change-Id: I58bae7535cfdb7dae419534179fe2e6256ec8d35
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3801
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

src/system/libroot/posix/glibc/libio/fileops.c

@@ -303,6 +303,11 @@ _IO_new_file_fopen(_IO_FILE *fp, const char *filename, const char *mode, int is3
 	case 'm':
 	  fp->_flags2 |= _IO_FLAGS2_MMAP;
 	  continue;
+#ifdef O_CLOEXEC
+	case 'e':
+	  oflags |= O_CLOEXEC;
+	  continue;
+#endif
 	default:
 	  /* Ignore.  */
 	  continue;