Revert "Use line-buffering on stdout, regardless of the output device."

This reverts commit e5028a4d83.

Line buffering for stdio is not implemented correctly on Windows, and
the _IOLBF option is equivalent to full buffering. Redirecting output
in bash with >& reproduces this problem.

ui/main.c

@@ -342,11 +342,6 @@ int main(int argc, char **argv)
 	struct cmdline_args args = {0};
 	int ret = 0;
 
-	/* Line buffering is required for tools which read mspdebug's
-	 * output (like msp430eclipse).
-	 */
-	setvbuf(stdout, NULL, _IOLBF, 0);
-
 	opdb_reset();
 	ctrlc_init();