Use build.d everywhere and take arguments by parameter ...

It seems easier to forward arguments from the build script this way,
and it's much more common to change the build arguments than the version.

Replace `build.sh` and `build.cmd` with `build.d` ...

Since dub needs a D compiler anyway, we might follow in DMD's step and use D for building,
as it is more reliable and expressive than a shell script as features pile up.

This unifies the two scripts to expose the same set of functionalities on all platforms,
with a behavior that is hopefully more sensible
(tradeoff and reasoning are explained through the code / documentation).
It is also completely independent from the current working directory.

Some discrepancies included:
- Name of the variable to override to select the compiler (DC vs DMD);
- Version file: Windows was always regenerating it;
- Version file: Windows would display "unknown" if `dub describe` failed,
  POSIX would use an empty string;
- Compiler detection: POSIX would detect ldmd2 / gdmd if dmd is not present,
  Windows would just fail;

All those functionalities are now unified in a single script.
The old script are kept for compatibility, but forward to the new script,
and can be removed in a few releases.

[build.sh] Use DFLAGS env variable to allow customizing the D compiler flags

Simplify build.sh: Drop obsolete libcurl specifics ...

According to the README, the min supported compiler version is v2.076.

implement $DUB build variable ...

fix localized import


do not escape DUB path

DUB_EXE in script environment

Use -flto=full for the release builds

Fix #555, tweak sed pattern in build.sh so that it properly checks the ...

DMD version for ldc also.

Remove -inline from the build script to side step CI failures.

Improve build options of the default build script. ...

Uses optimizations, but leaves assertions/contracts and adds debug information to not impede debugging on the user side. This can be considered progress in the direction of #862. It remains to be seen how much of a performance difference -release would make.

fix dub builds for FreeBSD ...

- curl workaround was linking against shared phobos library on FreeBSD (shipped since 2.069)
- fixed by moving pkg-config and LIBS stuff under <2.069.0 workaround

Use the existing version_.d if git fails in build.sh. ...

Also prints the version of the built binary for better default diagnostics.

Add Solaris configuration lines for LDC

allow specifying version in env variable to aid packaging

Increase minimum supported OS X version to 10.7. See #704.

gnu grep extensions aren't portable

fix dmd/ldmd2 detection in build.sh

don't link against curl with dmd >= 2.069.0 ...

- since Issue 13324 was implemented, libcurl is loaded at runtime
- avoids compatibility issues with versioned symbols in debian curl
  packages
- no longer requires libcurl-dev package

Remove unneeded export

Sets MACOSX_DEPLOYMENT_TARGET variable to avoid trivial incompatibility with OSX version earlier than the one used to build DUB

The default compiler should not depend on DUB's own build environment

use DMD to refer to dmd/gdmd/ldmd2 ...

- and keep DC for dmd/gdc/ldc2

don't build with debug and debug info ...

- fixes linking with ldc

fix build.sh for LDC

Use the actual binary name used to build DUB as the default compiler. See #303.

Add a DUB configuration to compile as a library without curl support.

Fix typo.

Fix build.sh for non-Linux systems.

Force the static version of Phobos for DMD/Posix.

Remove -property flag from build scripts.

Module statement addded to autogenerated version_.d