Bitcoin requires Berkeley DB 4.8 to be installed for portable wallets. get-bdb-4.8 is a simple script that downloads and installs BDB 4.8.
$ ./install.sh /path/to/bitcoin
BDB 4.8 is installed to the src/bdb folder in the path specified (in this case, /path/to/bitcoin/src/bdb). If no path is provided, BDB 4.8 installs locally to a new bdb folder.
If libtool is installed (and a configure.ac or configure.in file is present), the script will run autogen.sh (if needed), then configure the target directory to use the new BDB path:
$ autoreconf --install --force --prepend-include=/path/to/bitcoin/src/bdb/build_unix/build/include/
$ ./configure CPPFLAGS="-I/path/to/bitcoin/src/bdb/build_unix/build/include/" LDFLAGS="-L/path/to/bitcoin/src/bdb/build_unix/build/lib/"