Fixed Windows singleFile build mode issues ...

+ Fixed error with long command line when invoking the linker
+ Fixed object file naming

fixup #506 ...

- only use absolute initialCompilerBinary paths
- don't try to find absolute initialCompilerBinary in
  PATH

Fix: dub broken if compiled with absolute path DC ...

Code that was supposed to find working compiler always tried to
build absolute path from compiler name - even it was absolute
path already.

Use unique filenames for temporary files ...

Partial fix to #482

fix Issue 480 - default to available compiler ...

- search PATH for available compilers
- still prefer initialCompilerBinary (the one dub was build with)

Various small fixes ...

- fix computeBuildID for --compiler=/my/path;
- dub compiled with ldc tried to invoke ldc as default binary instead of ldc2;
- dmd: Don't generate anything;
- gdc: Do not link, only generate an object;

Merge pull request #387 from ibuclaw/gdcopts ...

Add some missing build options for gdc

faster determinePlatform ...

- 310ms -> 7ms

- don't link dub_platform_probe

- avoid phobos imports in the probe file

Add some missing build options for gdc

Merge pull request #380 from Geod24/ct-platform-probe ...

Make the platform probe the file at CT, hence allow it to work for cross-compilation.

Make the platform probe the file at CT, hence allow it to work for X compilation

Invoke the binary for linking, not the name

Add .def files to the list of source file types to pass to the linker.

Fix error message with LDC

Implement separate linking on gdc

Fix output flags for compilers != dmd

Add an explanation message for exit code -9. ...

This is a common enough issue to warrant a little diagnostic assistance (the compiler/linker process getting KILLed by the kernel due to out-of-memory).

Added singleFile support

Make prepareBuildSettings, extractBuildOptions and setTarget const

Use executeShell() to invoke the compiler. See #356. ...

execute() doesn't support running scripts with shebang lines. Still needs to be actually tested with a script on Linux/OS X.

Output all possible source/import files for "dub describe". Fixes #185. ...

Files that are not used for the current configuration or platform are output with an "unused" prefix (e.g. "unusedSource").

Ensure all files end with a newline

Use tabs in all JSON and D files

Removed trailing whitespace

Use "dub.json" instead of "package.json" in documentation

Ignore any noise on stdout when reading back the platform information.

Compilers: Add arch support for gdc

Fix suggestion text for -debug= dflags. See #310.

Remove debug log noise.

Put BuildSettings into its own module and invoke DMD to determine the actual build platform. ...

Currently only for DMD, the build platform is now determined by actually invoking the compiler with the proper -mX switches instead of guessing from the compiler run that was used to build DUB.