Download one Java binary file only when not building ia32 package

Since Java 7u10, upstream has stopped building ia32 package, and only
the binary file that matches the machine's architecture is required. So
make the script downloads that one only.

See: https://github.com/rraptorr/oracle-java7/commit/1591b3a6b2b2caefc9f0be690c9141372d4640bf
Merge pull request #81 from ladios/single_arch

No longer need both Java binary files for Java7