Fix type of argument 'argv'.
Addresses:
conv/conv_test.c:358:5: error: second parameter of 'main' (argument
array) must
be of type 'char **'
int main(int argc, char argv[])
Instead of using a ./configure parameter to decide whehter to build
tests or not, use the check_PROGRAMS variable so that the tests are
only built when running `make check`.
To avoid slowing down the test phase itself, collapse the declaration
of the test targets in the tests/Makefile.am file, this way they can
be built and linked in parallel before the testsuite is executed.
Signed-off-by: Diego Elio Pettenò <flameeyes@flameeyes.eu>