package/boost: boost-filesystem needs wchar

Also add reverse dependency for cc-tool.

Fixes:
http://autobuild.buildroot.net/results/2c7/2c7783b7f3cc28d54d15a7f017442c48244ffd8e/
http://autobuild.buildroot.net/results/2c7/2c7783b7f3cc28d54d15a7f017442c48244ffd8e/
http://autobuild.buildroot.net/results/0dd/0dd3ef96bbd034a41d908cdaa6552b27fda78132/
http://autobuild.buildroot.net/results/34b/34b55b2cd83fd5d87af4a9c15d05094b16ef3960/



and many more

Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>