Merge remote-tracking branch 'upstream/stable' into merge_stable

Don't reduce the max path length on Windows even further ...

Fixes #2143.

Add environment variables to BuildSettings (#2121)

Set cwd on spawn functions instead of chdir ...

It is more hygienic to use the cwd argument as it doesn't impact
the running process, and doesn't decouple the reason for it.

Remove redundant code with relativeTo ...

The versioned code was doing almost the same thing as relativeTo,
but adding `./` or equivalent so it could be run from the cwd.
Instead of doing this complicated patching, just use the absolute
path for running, but the relative path when issuing messages to the user.

Use compiler version, not frontend version for build IDs and paths ...

This prevents artifacts from being reused after upgrading the compiler
from a beta to a final or to a newer patch release.

cache the generated test main file: dub_test_root.d ...

these changes prevent dub from rebuilding a project every time it runs a unittest.

Replace occurences of 'in ref' with 'const scope ref' ...

In support for dlang/dmd#11000

Fix local cache

Remove some unused variables ...

There are plenty left, but those ones didn't seem to have any side effect.

Fix unnecessary rebuild of single file package

Include import paths in build ID. ...

Otherwise the same package with a different set of dependencies (or dependency versions) may get the same build ID, leading to linker errors.

Improve cross-compilation support (replace `version` checks by BuildPlatform runtime checks) ...

Also fixes #1249. For LDC as implicit cross compiler, the file
extensions for libraries and object files etc. don't depend on the
compiler, but solely on the target. Targets selected with `--arch` are
correctly probed by dub, so that the parsed `BuildPlatform` represents
the target platform.

Support separate linking with ldc2 ...

This is basically #1548 with an augmented set of compiler flags being
included in the linking command lines.

Use std.digest instead of the deprecated std.digest.digest.

Perform the tool chain checks based on the compiler name. ...

Gets rid of the additional methods in the Compiler interface and moves the checks to a more central location, since other generators apart from BuildGenerator might want to perform the checks in the future. Also keeps the API "package" for now to avoid adding insufficiently though-out public APIs.

Change toolchainRequirements fields to Dependency. ...

Also removes some API clutter from Compiler and PackageRecipe.

Merge pull request #1571 from rtbo/requirements ...

toolchainRequirements recipe support
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

toolchainRequirements recipe support

extraDependencyFiles attribute added

Merge pull request #1582 from andre2007/feature_pre_post_run_command ...

Pre/post run commands added
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

Fix temp copy files

Pre/post run commands added

Add basic support for 'building' target type "none" ...

See #97

Merge pull request #1286 from dlang/short_single_objects ...

Use shortened object file names in single-file build mode.
merged-on-behalf-of: Sebastian Wilzbach <sebi.wilzbach@gmail.com>

Selectively import crc32Of from std.digest.crc

Rename Path to NativePath. ...

Matches the changes done in vibe.d 0.8.x and vibe-core.

Make the code base compatible with vibe-core. ...

This still generates lots of deprecation warnings, but successfully compiles with vibe-core, as well as with the old vibe-d:core package.

Use shortened object file names in single-file build mode. ...

The full path was repeated twice in the object file path, resulting in excessively long paths (and failures on Windows). This change uses just the module name part (i.e. just the file *name* of the D file) and combines the path part as a single crc32 value (e.g. "somemod_0a56fb23.o").

Avoid passing linker files to a static library build command line. Fixes #1235.