dup2 requires a <unistd.h> include. Fixes the following when diffing config.log
when testing with a stricter compiler:
```
-warning: call to undeclared function 'dup2'; ISO C99 and later do not support
implicit function declarations [-Wimplicit-function-declaration]
+error: call to undeclared function 'dup2'; ISO C99 and later do not support
implicit function declarations [-Wimplicit-function-declaration]
```
---
aclocal.m4 | 3 +++
1 file changed, 3 insertions(+)
diff --git a/aclocal.m4 b/aclocal.m4
index cc97bd4b..25e20fc2 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -238,6 +238,9 @@ AC_CACHE_VAL(bash_cv_dup2_broken,
#include <sys/types.h>
#include <fcntl.h>
#include <stdlib.h>
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
int
main()
{
--
2.39.1
