When generating the correct inclusion directory for DEPEND, we mangled
it to be relative to the build or the source directory.  However, the
value we handle already come with a correct directory, so we only need
to use it as is.

Fixes #5543
Reviewed-by: NTim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5546)