xfsprogs: fix build with libunistring

xfsprogs: fix build with libunistring

The latest xfsprogs bump to version 4.15.1 added an optional dependency
on libunistring. Make sure we build libunistring before xfsprogs.

xfsprogs also added -lunistring to its make dependency. This does not
work very well with cross compilation because make does not know about
sysroot. Add a patch to remove this dependency.

To make shared only link with libunistring work, we also need to extend
the -static-libtool-libs patch to cover xfs_scrub as well.

Fixes:
http://autobuild.buildroot.net/results/66e/66e425b00a06f928be0951ac4196190fe88b0f62/
http://autobuild.buildroot.net/results/1cd/1cde87d1daf3c6009220ff47512794cef6a2938f/
http://autobuild.buildroot.net/results/8ba/8ba4e94cfbb8a5cbb166423a671bdbcdf535f86b/

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>