app-vim/youcompleteme: fix installation problem.

app-vim/youcompleteme: fix installation problem.

Error:
rm: cannot remove 'third_party/ycmd/libclang.so': No such file or directory
 * ERROR: app-vim/youcompleteme-99999999::gentoo failed (install phase):
 *   (no error message)
 *
 * Call stack:
 *     ebuild.sh, line 124:  Called src_install
 *   environment, line 4440:  Called die
 * The specific snippet of code:
 *       rm third_party/ycmd/libclang.so || die;

Actually:
$ ls third_party/ycmd
...
libclang.so.5
libclang.so.5.0

Closes: https://github.com/gentoo/gentoo/pull/8028