* tests/builders.scm (%bootstrap-inputs, %bootstrap-guile): New
variables.
("gnu-build"): Use them, by setting `#:implicit-inputs? #f' and `#:guile'.
* tests/packages.scm (%bootstrap-inputs, %bootstrap-guile): New
variables.
("trivial"): Pass `#:guile %bootstrap-guile'.
("GNU Hello"): Use `package-with-explicit-inputs' to use
%BOOTSTRAP-GUILE and %BOOTSTRAP-INPUTS.
* guix/store.scm (valid-path?): New procedure.
* tests/builders.scm ("http-fetch", "gnu-build"): Use it.
* tests/derivations.scm ("add-to-store, flat", "add-to-store,
recursive", "derivation with no inputs", "build derivation with 1
source", "build derivation with coreutils",
"build-expression->derivation with expression returning #f"):
Likewise.
* guix/derivations.scm (build-expression->derivation): Change to expect
INPUTS to have the form (NAME DRV-PATH SUB-DRV) or (NAME DRV-PATH),
instead of (NAME . DRV-PATH). Update callers accordingly.
* guix/gnu-build-system.scm, tests/builders.scm, tests/derivations.scm:
Update accordingly.
* guix/derivations.scm (build-expression->derivation): Add all of INPUTS
as inputs to the final derivation.
* guix/build/gnu-build-system.scm, guix/build/utils.scm,
guix/gnu-build-system.scm: New files.
* tests/builders.scm ("gnu-build"): New test.
* guix/derivations.scm (imported-modules): New procedure.
(build-expression->derivation): New keyword argument `modules'.
Use `imported-modules' when MODULES is non-empty, and pass it with
`-L' to GUILE.
* guix/build/http.scm, guix/http.scm, tests/builders.scm: New files.
