Add script to print build environment info. (#539)

* Add script to print build environment info.

The new script is also included in:
- all.sh
- basic-build-test.sh

* Tidy up environment reporting script.

Changes include:
- making the echo calls portable
- removing unnecessary brackets
- using more efficient checks for the existance of commands
- correcting typos and copyright year

* Update references to output_env.sh

tests/scripts/all.sh

@@ -121,6 +121,9 @@ fi
 #
 # Indicative running times are given for reference.
 
+msg "info: output_env.sh"
+scripts/output_env.sh
+
 msg "test: recursion.pl" # < 1s
 tests/scripts/recursion.pl library/*.c