Similar to the change to driver.makefile to handle multiple architectures,
we use make's default behaviour to fail a task if any dependency fails.

These were intended originally to allow a hybrid build system: you
could build an e3 module as the dynamically loaded shared library,
but you could also run `make epics` and build it as a vanilla EPICS
module.

However, this has never really worked, nor has it been supported. It
may in the future be supplanted by properly using the EPICS build
rules in lieu of the use of driver.makefile, but that is for a future
change.

The test rule for e3 modules actually does a cellinstall and run the
tests inside this temporary installation. The cellinstall needs to
overwrite some path variables to work this variables were not accessible
through the test rule as they are just changed if cell is on
MAKECMDGOALS. This made impossible to use the standard path variables
inside module's custom test rules.

To fix it the same mechanism used in cellinstall is implemented for test
and the variables paths are now overwritten. This makes possible ie. to
use E3_MODULES_INSTALL_LOCATION_BIN inside custom test rules.

This commit also introduces an unwanted behavior. As the test rule is
now overwriting the standard path variables it cannot longer be along
with the install rule. For example, running `make test install` will
install the module inside the test dir. This is a known issue for
cellinstall as well and a restructure of the Makefile code should be
made to isolate the rules.

remove inclusion of the run_iocsh script and change tests and targets accordingly; idea is that run-iocsh is a required package but not part of require per se