In 'build.sh', both '=' and '==' are used for testing string equality of strings. When running build.sh on Ubuntu 13.04(and other Debian-based distros which use 'dash' for the default implementation of sh), the use of '==' results in the following:
./build.sh: 4: [: amo: unexpected operator
./build.sh: 4: [: staging: unexpected operator
./build.sh: 7: [: test: unexpected operator
Creating working directory ...
Creating scriptish-2013.07.30.beta.xpi ...
Cleaning up temporary files ...
./build.sh: 60: [: amo: unexpected operator
./build.sh: 60: [: staging: unexpected operator
Solution: replace uses of '==' with '=' on lines 4, 7 and 60 in build.sh
Closes #165 == -> = and removing the staging build