configure.ac: remove Bashisms
The test
built-in does not define an ==
operator in POSIX shell.
Pretending that it does leads to runtime errors when /bin/sh
is not
Bash.
Example when /bin/sh
is Dash:
./configure: 6225: test: x: unexpected operator
./configure: 6239: test: x: unexpected operator
./configure: 6266: test: xyes: unexpected operator
./configure: 6273: test: xno: unexpected operator
./configure: 6290: test: xyes: unexpected operator
./configure: 6308: test: xno: unexpected operator
These errors do not cause configure
to fail outright, but they prevent
correct detection of features.