qt4: remove trailing slash from prefix

qt4: remove trailing slash from prefix

The trailing slashs on "Prefix=${prefix}/" and "-prefix ${prefix}/" are passed
through to the generated pkgconfig files and may be joined to paths like
"/include" yielding a final path with a double forward-slash (eg.
"/usr//include"). This may end up in the debugging symbols in other applications
or libraries which depend on qt4 which in turn causes the debugedit program to
fail with the message "canonicalization unexpectedly shrank by one character"
when it tries to replace the double forward-slash with a single forward-slash.
Thus the function split_and_strip_files fails and ultimately do_package fails.

As this slash is removed from the prefix it is added into the regular expression
used to fix up pkgconfig files later in the recipe.

This error was seen in vlc in meta-openembedded and should be solved by this
change in openembedded-core.

(From OE-Core rev: 61a7329a5c1f0b84f447256134f5a77917f07f38)

Signed-off-by: Paul Barker <paul@paulbarker.me.uk>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>