fix to MCOL-2110 Cant build engine out-of-source

[djmott]

Prefixing SERVER_BUILD_INCLUDE_DIR and SERVER_SOURCE_ROOT_DIR with CMAKE_BINARY_DIR works in the case of the engine and server build folders being siblings to each other and relative paths supplied to cmake. If the build folders are not siblings and absolute paths are supplied to cmake it fails. Using GET_FILENAME_COMPONENT will resolve the correct path in both cases.

[djmott]

I am submitting this patch under the BSD-new license.

[drrtuy]

Greetings David.
Thank you for the contribution we appreciate your support.
The change makes our buildbot b/c it didn't account for the change. We will look into this problem.

[djmott]

Sorry I didn't mean to make work for you. Building out-of-source according to the README.md worked for me also building from within subdirectories of the respective projects while passing absolute paths of the servers artifacts to cmake for the engine. I use some tools that need cmake configured this way. I'll take a look and try to replicate. If its a problem just don't merge, I'm happy just keeping it local.

The interesting CI steps are shell and shell_6:
shell:
PWD=/data/buildbot/bb-worker/centos6_PR/build/mariadb-columnstore-server
cmake ../../mariadb-columnstore-server

shell_6:
PWD=/data/buildbot/bb-worker/centos6_PR/build/mariadb-columnstore-engine
cmake ../../mariadb-columnstore-engine -DSERVER_BUILD_INCLUDE_DIR=../mariadb-columnstore-server/include -DSERVER_SOURCE_ROOT_DIR=../../mariadb-columnstore-server'

...

SERVER_BUILD_INCLUDE_DIR = /data/buildbot/bb-worker/centos6_PR/mariadb-columnstore-server/include
SERVER_SOURCE_ROOT_DIR = /data/buildbot/bb-worker/mariadb-columnstore-server

[djmott]

I see, it's expecting the the paths to be relative to CMAKE_CURRENT_BINARY_DIR instead of CMAKE_CURRENT_LIST_DIR. It works according to README.md because the relative paths to the server artifacts in SERVER_BUILD_INCLUDE_DIR are the same. I'll fix.

[drrtuy]

It looks great now.