Use better variable names in dev mode test

[turkeylurkey]

BaseDevTest and DevTest classes use variables named buildDir and targetDir. These names are confusing because they are not used consistently with other parts of the ci.gradle project.

In these tests buildDir refers to the project directory so projectDir might be more appropriate.

targetDir refers to the output directory like in a Maven project. In a Gradle project such as this one, buildDir is the preferred name for this concept since the output directory is actually called build.