If the CONF_XML environment variable is set, use that conf.xml file instead of the standard $PAPARAZZI_HOME/conf/conf.xml
Meaning you can run tests for a different conf without changing the conf.xml symlink, e.g.
```
CONF_XML=$PAPARAZZI_HOME/conf/conf_tests.xml prove tests/examples
```
Examples on how to test compile all aircrafts/targets in your current conf.xml:
with parallel compilation and showing full output during compilation
$ J=AUTO prove tests/examples -v
only showing full compile output if there has been an error, if there were warnings only print those
$ SHOW_WARNINGS_ONLY=1 prove test/examples
with parallel compilation and treating all warnings as errors:
$ J=AUTO USER_CFLAGS=-Werror prove tests/examples
Also replace LOCAL_CFLAGS (which wasn't used anymore) with USER_CFLAGS (and add where missing).
Now you can e.g. test compile all aircrafts/targets in your conf and add extra flags like treating warnings as errors:
$ J=AUTO USER_CFLAGS=-Werror prove conf/examples
Check exit status instead of whether output contains the word Error.
With ForceArray on xmlSimple no need to check for target separately.
Also don't filter on list of firmwares, build all..
make AIRCRAFT=BOOZ2 clean_ac nps.compile
make AIRCRAFT=LisaLv11_Aspirinv15_Overo_RC clean_ac nps.compile
make AIRCRAFT=LisaLv11_Booz2v12_RC clean_ac nps.compile
make AIRCRAFT=Quad_LisaM_2 clean_ac nps.compile
Adding the XML::Simple perl module into the tests/lib directory so that
normal users don't need to install it to run the tests.
Reformatted the conf/conf.xml.example file to not all be on single
lines for each config since this is now not required as we're parsing
the XML.
Felix Ruess
Bernard Davison