DX_PROG_FLEX: redirect lex output to the log file.

AIX 7.2 includes a "lex" program which prints error messages to standard
output.  So ensure that is also redirected to the log file, otherwise
we get a bunch of garbage printed to the terminal when configuring.

diff --git a/m4/flex.m4 b/m4/flex.m4
index 419efbd9ef1131249d233b5cb5a7a15360542c8b..bc9998535bdd9b693ef1791ed6be6257c16faa3d 100644 (file)
--- a/m4/flex.m4
+++ b/m4/flex.m4
@@ -1,4 +1,4 @@
-dnl Copyright © 2020-2021 Nick Bowler
+dnl Copyright © 2020-2021, 2024 Nick Bowler
 dnl
 dnl License WTFPL2: Do What the Fuck You Want To Public License, version 2.
 dnl This is free software: you are free to do what the fuck you want to.
@@ -72,6 +72,6 @@ int main(void)
 }])
 
 AC_DEFUN([_DX_FLEX_DO_TEST], [rm -f conftest.c
-AS_IF([$1 -o conftest.inc conftest.l 2>&AS_MESSAGE_LOG_FD],
+AS_IF([$1 -o conftest.inc conftest.l >&AS_MESSAGE_LOG_FD 2>&1],
 [AC_LINK_IFELSE([AC_LANG_SOURCE([[#include "conftest.inc"]])], [$2], [$3])],
 [$3])])