make fails when a unit test fails.

The ALL_UNIT_TESTS_COMMAND was building the list of commands to run in this way:
test1;test2;test3
The semicolon makes the shell go on even if a command fails. Make would only get
the result of the last command.
I changed the list to:
test1 && test2 && test3
This will make the shell bail as soon as a test fails and make will get the correct
exit status.