gnu: Add a "debug" output for some packages.

* gnu/packages/base.scm (coreutils, gnu-make, glibc): Add a "debug" output.
* gnu/packages/bdw-gc.scm (libgc): Likewise.
* gnu/packages/guile.scm (guile-2.0): Likewise.
* gnu/packages/libffi.scm (libffi): Likewise.
* gnu/packages/multiprecision.scm (gmp, mpfr, mpc): Likewise.

build-system/gnu: Write debug files to the "debug" sub-derivation, if any.

* guix/build/gnu-build-system.scm (strip): Add `objcopy-command' keyword
  parameter.
  [debug-output, debug-file-extension]: New variables.
  [debug-file, make-debug-file, add-debug-link]: New procedures.
  [strip-dir]: Use them.

utils: Re-export `alist-cons' and `alist-delete'.

* guix/build/utils.scm: Re-export `alist-cons' and `alist-delete'.

gnu: gcc: Use `gcc-configure-flags-for-triplet' when cross-compiling GCC.

* gnu/packages/cross-base.scm (gcc-configure-flags-for-triplet): Move to...
* gnu/packages/gcc.scm (gcc-configure-flags-for-triplet): ... here.  New
  procedure.
  (gcc-4.7): Use it when (%current-target-system) is true.

build: Add "mips64el-linux-gnuabi64" as a cross build target.

* build-aux/hydra/gnu-system.scm (%packages-to-cross-build): Add
  %bootstrap-tarballs.
  (%cross-targets): Add "mips64el-linux-gnuabi64".

gnu: cross-base: Add support for `mips64el-linux-gnu-gnuabi64' (N64 ABI).

* gnu/packages/cross-base.scm (gcc-configure-flags-for-triplet): New
  procedure.
  (cross-gcc): Use it.
  (xgcc-mips64el): Use *-gnuabi64 instead of the N32 ABI.

gnu: make-bootstrap: Fix cross compilation of binutils-static.

* gnu/packages/make-bootstrap.scm (%binutils-static): Inherit configure
  flags from BINUTILS.

gnu: make-bootstrap: Have %gcc-static actually static when cross building.

* gnu/packages/make-bootstrap.scm (%gcc-static): Pass `-static' through
  `LDFLAGS' when cross-compiling.

gnu: gcc: Allow cross-compilation of GCC itself.

* gnu/packages/gcc.scm (gcc-4.7): Define `CC_FOR_TARGET',
  `AR_FOR_TARGET', etc. when cross-compiling.

gnu: cross-base: Make `glibc-dynamic-linker' do the right thing.

* gnu/packages/bootstrap.scm (glibc-dynamic-linker): Determine SYSTEM
  based on (%current-target-system) when it's true.
* gnu/packages/cross-base.scm (cross-gcc): Directly call
  (package-arguments gcc-4.7) from the body of `arguments'.

gnu: cross-base: Build Binutils with `--with-sysroot=/'.

* gnu/packages/cross-base.scm (cross-binutils): Use `--with-sysroot=/'.

build: Build the bootstrap tarballs on Hydra.

* build-aux/hydra/gnu-system.scm (%packages-to-cross-build): Uncomment
  the bootstrap tarball packages.

gnu: make-bootstrap: Allow cross-compilation of the bootstrap tarballs.

* gnu/packages/make-bootstrap.scm (package-with-relocatable-glibc): Turn
  `inputs' into a thunk.  Add `native-inputs', and pass it to
  `package-with-explicit-inputs'.
  (%static-inputs): Add %BASH-STATIC as an input to gawk when cross
  building.
  (%glibc-stripped): When cross compiling,
  use (glibc-for-bootstrap (cross-libc)) as the basis.
  (%gcc-static): Base on GCC-4.7, not GCC-FINAL.
  (tarball-package): TAR and XZ are native inputs.  Choose the tarball
  file name based on (%current-target-system) too.

build-system/gnu: `package-with-explicit-inputs' skips non-GBS packages.

* guix/build-system/gnu.scm (package-with-explicit-inputs)[rewritten-input]:
  Leave P unchanged if its build system is not GNU-BUILD-SYSTEM.

gnu: cross-base: Make the cross tools native inputs.

* gnu/packages/cross-base.scm (cross-gcc): Change `inputs' to
  `native-inputs', and set `inputs' to the empty list.
  (cross-libc): Likewise.

build-system/gnu: Augment `package-with-explicit-inputs' for cross builds.

* guix/build-system/gnu.scm (package-with-explicit-inputs): Add
  `native-inputs' keyword parameter.  Allow INPUTS and NATIVE-INPUTS to
  be thunks.

build-system/trivial: Don't bind `%target' in the builder.

* guix/build-system/trivial.scm (trivial-cross-build): Don't bind
  `%target' here since this causes problem when BUILDER
  contains (use-modules ...) clauses, and can be achieved differently
  anyway.

gnu: gawk: Allow cross-compilation.

* gnu/packages/gawk.scm (gawk)[arguments]: Annihilate the
  `check-for-shared-lib-support' target when cross-compiling.

build-system/gnu: Disable test suite when cross building.

* guix/build-system/gnu.scm (gnu-cross-build): Change #:tests? to
  default to #f.

gnu: libffi: Upgrade to 3.0.13.

* gnu/packages/libffi.scm (libffi): Upgrade to 3.0.13.