packages: Pass `system' around.

* guix/packages.scm (package-source-derivation): Add `system'
  parameter.  Pass it to METHOD.
  (package-derivation)[expand-input]: Pass SYSTEM to
  `package-derivation' and `package-source-derivation'.

* distro/packages/base.scm (package-with-bootstrap-guile)[boot]: Pass
  SYSTEM to FETCH.

derivations: Make sure `build-expression->derivation' & co. pass `system'.

* guix/derivations.scm (imported-files): Call
  `build-expression->derivation' with SYSTEM, not (%current-system).
  (build-expression->derivation): Pass SYSTEM to `imported-modules' and
  `compiled-modules'.

derivations: Pass the derivation of guile-for-build to `imported-files' & co.

* guix/derivations.scm (%guile-for-build): Initialize to #f.
  (imported-files, imported-modules, compiled-modules): Add `guile'
  keyword parameter.  Pass it down to `build-expression->derivation'.
  (build-expression->derivation)[guile-drv]: New variable.  Pass it as
  the #:guile parameter for `imported-modules' and `compiled-modules'.

* tests/derivations.scm: Set %GUILE-FOR-BUILD to the derivation of
  %BOOTSTRAP-GUILE.

distro: Build the final inputs against the final Bash, not the bootstrap Bash.

* distro/packages/base.scm (%boot4-inputs): New variable.
  (guile-final): Use it.
  (%final-inputs): Build with %BOOT4-INPUTS, not %BOOT3-INPUTS.

distro: ncurses: Don't patch shebangs.

* distro/packages/base.scm (ncurses): Pass #:patch-shebangs? #f.

distro: Bootstrap using our own binaries instead of those from Nixpkgs.

* distro/packages/base.scm (%bootstrap-inputs): Switch to using our own
  bootstrap binaries instead of those from Nixpkgs.

distro: Build glibc with `--enable-obsolete-rpc'.

* distro/packages/base.scm (glibc-final): Pass `--enable-obsolete-rpc'.
  (%bootstrap-glibc): Update hash accordingly.

distro: Add missing Linux-Libre headers to the bootstrap glibc.

* distro/packages/base.scm (%glibc-stripped): Copy all of Linux-Libre's
  `include/asm' directory; copy a few linux/ headers too.
  (%bootstrap-glibc): Update tarball hash.

distro: Add a bootstrap GCC that uses binaries from the tarball.

* distro/packages/base.scm (%bootstrap-gcc): New variable.

Add `guix-download'.

* guix-download.in: New file.
* configure.ac: Emit `guix-download' and make it executable.
* Makefile.am (bin_SCRIPTS): Add `guix-download'.
* po/POTFILES.in: Add `guix-download.in'.

store: Add `query-path-hash'.

* guix/store.scm (write-arg, read-arg): Add `base16' literal and
  corresponding rule.
  (query-path-hash): New operation.

* tests/derivations.scm ("fixed-output derivation"): Check whether
  `query-path-hash' returns a bytevector.

distro: Add missing commands in the bootstrap binaries.

* distro/packages/base.scm (%static-inputs): Add an `awk' -> `gawk', and
  `sh' -> `bash' symlinks.  Add `fgrep' and `egrep'.
  (%bootstrap-coreutils&co): Use new tarball that contains that
  symlink.

* distro/packages/bootstrap/x86_64-linux/bash,
  distro/packages/bootstrap/x86_64-linux/mkdir,
  distro/packages/bootstrap/x86_64-linux/tar,
  distro/packages/bootstrap/x86_64-linux/xz: Use binaries from that
  tarball (the previous binaries hadn't gone through
  `remove-store-references', which is fixed now.)

guix-build: Change `--local-build' to `--no-substitutes'.

* guix-build.in (%default-options): Add `substitutes?'.
  (show-help): Change `--local-build' to `--no-substitutes'.
  (guix-build): Adjust accordingly.

distro: Update file name of initial Binutils tarball.

* distro/packages/base.scm (%bootstrap-binutils): Update remote file
  name.

derivations: Compile the #:modules passed to `build-expression->derivation'.

* guix/derivations.scm (imported-files)[parent-dirs]: Move to...
  (parent-directories): ... here.  New procedure.
  (compiled-modules): New procedure.
  (build-expression->derivation): Use it.

* tests/derivations.scm ("build-expression->derivation with modules"):
  New test.

distro: Update bootstrap glibc package.

* distro/packages/base.scm (%bootstrap-glibc): Update initial regexp to
  make it less Nixish.  Update hash to new tarball.

distro: Add required Linux-Libre headers to the glibc tarball.

* distro/packages/base.scm (%glibc-stripped): Include required headers
  from Linux-Libre.

distro: gcc: No longer store the absolute path of crt files.

* distro/packages/base.scm (gcc-4.7): Define
  STANDARD_STARTFILE_PREFIX_[12] instead of storing the absolute path of
  crt files.

distro: Fix GCC tarball to include the `libexec' directory.

* distro/packages/base.scm (%gcc-stripped): Copy $gcc/libexec to $out.

distro: Fix glibc tarball to include *.so.*.

* distro/packages/base.scm (%glibc-stripped): Fix regexp to
  include *.so.* in the output.