Add unittest to test collection of C sources and headers

reduce dependency on the working directory ...

Improves library API usage and bugs with the build generator

Reduce dependency on `std.file` (#2547)

Posix: Add default SONAME/install_name for dynamic libraries ...

Setting it to the filename (ELF) or `@rpath/<file name>` (Mach-O).

This seems to be required in order to use the libraries copied to
the output directory of dependees - either by setting the
LD_LIBRARY_PATH env var when starting the executable, or baking a
RUNPATH into the executable (e.g., via `patchelf --set-rpath` for
deployment).

Otherwise the loader tries to load the library from the original
location specified in the linking cmdline, which is some
`<path to dep pkg>/.dub/…` path (and apparently potentially
relative, and thus even more brittle). For ELF, I would assume
that all SONAME + DT_NEEDED entries (of executable + all .so libs)
would need to be post-processed to enable loading the libs from the
executable's directory (well, any non-original location).

Forward flag `--color={on,off}` to compiler calls (#2382) ...

When the user sets the color mode explicitly,
we forward it to the compiler for consistency,
while making sure it doesn't impact the build cache ID.

Keep logging functionality out of the public API as requested in https://github.com/dlang/dub/pull/2124#issuecomment-813016939.

New logging module - initial functionality ...

The new module replaces dub.internal.vibecompat.core.log by using the
same function names, but implementing colored output and the left
fixed-width tag. Overloaded functions are provided to output colored
text.

Still missing initLogging() and non-TTY stdout/stderr detection

compilers: Change lflagsToDFlags to avoid scope escape ...

If 'in' implies 'scope', then the parameter is being escaped.

Refactor checks for platform is Windows into a method on BuildPlatform

Merge pull request #2186 from ibara/gdc-betterC ...

Add -fno-druntime to GDC BuildOptions; it is the betterC flag.

add UnsupportedArchitecture/CompilerException ...

for API purposes to not match on string prefixes

Tweak additional flags at Iain's recommendation: ...

-fd-verbose becomes -v
-fdebug-c doesn't exist, remove (-g is still there)
-fXf= becomes -Xf
Replace -O3 with -O2

Add -fno-druntime to GDC BuildOptions; it is the betterC flag.

Add environment variables to BuildSettings (#2121)

Remove unused imports.

Remove unused selective imports. These are private imports of symbols that do not occur elsewhere in the file, so they are safe to be removed.

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

In support for dlang/dmd#11000

gdc: Build dub_platform_probe with -fsyntax-only

Add support for iOS/tvOS/watchOS

[dip1000] Fix compilation and test it on Travis CI

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.

fix #1003 - Check empty ldflags

Use -dumpfullversion to determine GDC version

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.

toolchainRequirements recipe support

Fix dynamicLibrary extensions on OSX. Fixes #1228

Rename Path to NativePath. ...

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

Refactor determinePlatform, determineArchitecture, and determineCompiler from dub.platform into strings that can be pasted into generatePlatformProbeFile and remove unused imports.

use GDC's -S flag to avoid creating an object file