ui: Tweak conflicting profile entry error message.

* guix/ui.scm (call-with-error-handling): Use 'manifest-entry-output*'
when reporting conflicting profile entries.

profiles: Really disable deprecation warnings for 'profile-derivation'.

This is a followup to 2815fca1423cf72e6f3d0e774f1058bcbf8dfdbf.

* guix/profiles.scm (profile-derivation)[builder]: Remove
'debug-disable' call, which was ineffective.
Pass #:env-vars to 'gexp->derivation'.

scripts: Default to Guile 2.2 as the guile-for-build.

* guix/scripts/environment.scm (guix-environment): '%guile-for-build'
now defaults to GUILE-2.2 instead of GUILE-2.0.
* guix/scripts/package.scm (guix-package): Likewise.
* guix/scripts/pull.scm (guix-pull): Likewise.

profile: Use _IO* but disable deprecation warning.

This fixes a regression introduced in
2f60084f77815f454d1521396c2a383390ea2865, whereby the profile derivation
would fail to run on Guile 2.0 (as is the case with "guix package
--bootstrap").

Reported by Christopher Baines.

* guix/profiles.scm (profile-derivation)[builder]: Use _IO* but add
'debug-disable' call.

profiles: Avoid _IO* in profile builder.

* guix/profiles.scm (profile-derivation)[builder]: Avoid the deprecated
_IO* constants.

profiles: Do not import the host's srfi-{19,26}.scm files.

Previously the "manual-database" derivation would always import the
host's srfi-{19,26}.scm files in the build side.  In practice this means
that different users could get different manual-database.drv depending
on the Guile version they're using in the host.

For example, the (gnu tests install) tests would fail if the host was
running Guile 2.2.3 because the guest is running 2.2.2, and thus has
different srfi-{19,26}.scm files.  The manual-database.drv would need to
be built from source, which would fail because prerequisites were
missing.

Reported by Mathieu Othacehe <m.othacehe@gmail.com>
at <https://debbugs.gnu.org/cgi/bugreport.cgi?bug=29409#96>.

* guix/profiles.scm (manual-database): Do not pass #:modules to
'gexp->derivation'.  Wrap 'build' gexp in 'with-imported-modules' form.

Do not set '%fresh-auto-compile'.

* guix/scripts/offload.scm (build-machines): Comment out
'(set! %fresh-auto-compile #t)' since with Guile 2.2.3 it could lead to
an actual rebuild of everything that gets loaded from there on.  See
<https://bugs.gnu.org/29226>.
* guix/ui.scm (load*): Likewise.

records: Use 'make-struct/no-tail'.

* guix/records.scm (make-syntactic-constructor): Use
'make-struct/no-tail' as 'make-struct' is deprecated as of 2.2.3.

guix system: 'init' displays a progress bar while copying.

Until now it would print the name of each store item being copied, which
was verbose and unhelpful.

* guix/scripts/system.scm (copy-closure): Use 'progress-reporter/bar'
and 'call-with-progress-reporter'.
(guix-system): Parameterize 'current-terminal-columns'.

guix system: Simplify closure copy.

* guix/scripts/system.scm (copy-item): Add 'references' argument and
remove 'references*' call.  Turn into a non-monadic procedure.
(copy-closure): Remove initial call to 'references*'.  Only pass ITEM to
'topologically-sorted*' since that's equivalent.  Compute the list of
references corresponding to TO-COPY and pass it to 'copy-item'.

weather: Use (guix progress) for progress report.

* guix/progress.scm (start-progress-reporter!, stop-progress-reporter!)
(progress-reporter-report!): New procedures.
* guix/scripts/weather.scm (call-with-progress-reporter): New procedure.
(package-outputs)[update-progress!]: Remove.
Use 'call-with-progress-reporter' instead.
(guix-weather): Parameterize 'current-terminal-columns'.

progress: Add 'progress-reporter/bar'.

* guix/progress.scm (progress-reporter/bar): New procedure.

progress: 'progress-bar' accounts for brackets.

* guix/progress.scm (progress-bar): Subtract 2 to BAR-WIDTH to account
for brackets.

progress: Factorize erase-in-line.

* guix/progress.scm (erase-in-line): New procedure.
(progress-reporter/file): Use it.

utils: Add target-arm32? procedure.

* guix/utils.scm (target-arm32?): New exported procedure.

ui: Present 'use-modules' hints with a question mark.

Suggested by myglc2 <myglc2@gmail.com>.

* guix/ui.scm (report-load-error): Write "Did you forget" rather than
"Try adding."

build-system: Add scons-build-system.

* guix/build-system/scons.scm: New file.
* guix/build/scons-build-system.scm: New file.
* Makefile.am (MODULES): Register them.
* doc/guix.texi (Build Systems): Add scons-build-system.

gexp: Default to 'guile-2.2' for 'program-file'.

Previously things returned by 'program-file', such as %MODPROBE-WRAPPER
in (gnu services), would refer to 'guile-final'.  This would introduce
'guile-final' in the system closure, which is otherwise absent.  By
referring to 'guile-2.2' we remove that extra Guile.

* guix/gexp.scm (default-guile): Refer to GUILE-2.2 instead of
GUILE-FINAL.

gexp: 'compiled-modules' disables deprecation warnings by default.

This avoids repeated deprecation messages, particularly while running
'guix system build' or similar.

* guix/gexp.scm (gexp->derivation): Add #:deprecation-warnings.  Pass it
to 'compiled-modules'.
(compiled-modules): Add #:deprecation-warnings and honor it.
* doc/guix.texi (G-Expressions): Update 'gexp->derivation'
documentation.
* guix/packages.scm (patch-and-repack): Pass #:deprecation-warnings #t.

lint: Adjust file-name length test for out-of-tree file names.

* guix/scripts/lint.scm (check-patch-file-names): Adjust
file-name-length calculation.