Bug 12518 – Add ability to not rebuild the project on file with custom build tool change

There are two general cases: 1. The file output is only linked with the project (e.g. *.h or *.rc file generating a *.res file). Here only relink is needed, no recompiling. 2. The file output is just put into the target directory (e.g. program configuration file). This file should be only copied, no building action should be preformed. As a solution I suggest to make "Add output to link" checkbox forcing a #1 behaviour and add "External file" or "Not cause rebuild" checkbox for #2 one. It will be also useful to make it easy to mark file for just copying to target directory.

Makes sense to not force a compile and link step if a custom rule does not contribute to the link. Splitting compile and link into separate steps is a bit more work as it needs other dependency checks. A custom build step might also contribute to compilation (e.g. by generating a string import file). Regarding #2: How about adding a build tool "Copy", that could also update the modification date of the target?

regarding 2: 0.3.39 now has a new option "assume outout uptodate with same time" for the custom build tool.

> 1. The file output is only linked with the project (e.g. *.h or *.rc file > generating a *.res file). > Here only relink is needed, no recompiling. https://github.com/dlang/visuald/releases/tag/v0.45.0-beta1 now uses two separate steps (with their own set of dependencies) if anything but "combined" compilation is used.