Fix broken firebreath-boost install

The glob pattern was causing multiple slashes in the path being used to install the firebreath-boost files, which resulted in "No such file or directory" errors. (Possibly only on Windows.)

Here is the relevant log data from the console when running prep2012.cmd from the command line:

	Using 7-zip to extract the archive
	Installing firebreath-boost...
	CMake Error at cmake/common.cmake:299 (file):
	  file RENAME failed to rename

		C:/Users/stevenlybeck/Documents/projects/BrowserPlugin/firebreath/src/3rdParty/boost/firebreath-firebreath-boost-4bc2ed3//libs

	  to

		C:/Users/stevenlybeck/Documents/projects/BrowserPlugin/firebreath/src/3rdParty/boost/libs

	  because: No such file or directory