Gotchas and incompatibilities in build script

[logological]

The build.sh script is not written in a way that will work with all Bourne-compatible shells, and uses globbing in dangerous ways. In particular:

• Commands such as echo "-u:enable update" can be misinterpreted as passing a command-line parameter to echo
• Globbing in lines such as zip -r exchangecalendar-v$version.xpi * … could end up passing command-line parameters to zip if there exist filenames starting with a hyphen
• Variable substitution in lines such as zip -r exchangecalendar-v$version.xpi … could result in unwanted word splitting, depending on the value of $version.

[advancingu]

Merged.