Don't use non-portable operator "==" in configure.ac
The test operator == is a Bash extension and produces a wrong result
if /bin/sh is not Bash. This happens on NetBSD for example:
% /bin/sh
$ test 8 == 8
test: ==: unexpected operator
$ echo $?
2The test operator == is a Bash extension and produces a wrong result
if /bin/sh is not Bash. This happens on NetBSD for example:
% /bin/sh
$ test 8 == 8
test: ==: unexpected operator
$ echo $?
2