Some small remarks:

On Sun, 2021-04-11 at 15:46 +0200, Ludovic Courtès wrote:
> 
> [...]
> @@ -7307,6 +7307,84 @@ Coreutils, Bash, Make, Diffutils, grep, and sed (see the @code{(guix
>  build-system gnu)} module for a complete list).  We call these the
>  @dfn{implicit inputs} of a package, because package definitions do not
>  have to mention them.
> +
> +This build system supports a number of keyword arguments, which can be
> +passed @i{via}

Why the italics?  I've heard some people italicise "via" because it's a foreign
word (from Latin), but I'm not convinced.  I don't see anyone italicising
"broccoli", even though it is Italian (going by
https://en.wiktionary.org/wiki/broccoli).

>  the @code{arguments} field of a package.  Here are some
> +of the main parameters:
> +
> +@table @code
> +@item #:phases
> +This argument specifies build-side code that evaluates to an alist of
> +build phases.  @xref{Build Phases}, for more information.
> +
> +@item #:configure-flags
> +This is a list of flags (strings) passed to the @command{configure}
> +script.  @xref{Defining Packages}, for an example.
> +
> +@item #:make-flags
> +This list of strings contains flags passed as arguments to
> +@command{make} invocations in the @code{build}, @code{check}, and
> +@code{install} phases.
> +
> +@item #:out-of-source?
> +This Boolean,
‘Boolean’ is miscapitalised.

>  @code{#f} by default, indicates whether to run builds in a
> +build directory separate from the source tree.
> +
> +When it is true, the @code{configure} phase creates a separate build
> +directory, changes to that directory, and runs the @code{configure}
> +script from there.  This is useful for packages that require it, such as
> +@code{glibc}.
> +
> +@item #:tests?
> +This Boolean, @code{#t} by default, indicates whether the @code{check}
> +phase should run the package's test suite.

Likewise (miscapitalised).
> +@item #:test-target
> +This string, @code{"check"} by default, gives the name of the makefile
> +target used by the @code{check} phase.
> +
> +@item #:parallel-build?
> +@itemx #:parallel-tests?
> +These Boolean values specify whether to build, respectively run the test
Likewise (miscapitalised).
> +suite, in parallel, with the @code{-j} flag of @command{make}.  When
> +they are true, @code{make} is passed @code{-j@var{n}}, where @var{n} is
> +the number specified as the @option{--cores} option of
> +@command{guix-daemon} or that of the @command{guix} client command
> +(@pxref{Common Build Options, @option{--cores}}).
> +
> +@cindex RUNPATH, validation
> +@item #:validate-runpath?
> +This Boolean, @code{#t} by default, determines whether to ``validate''
Likewise (miscapitalised).

> +the @code{RUNPATH} of ELF binaries (@code{.so} shared libraries as well
> +as executables) previously installed by the @code{install} phase.
> +
> +This validation step consists in making sure that all the shared
> +libraries needed by an ELF binaries, which are listed as
> +@code{DT_NEEDED} entries in its @code{PT_DYNAMIC} segment, appear in the
> +@code{DT_RUNPATH} entry of that binary.  In other words, it ensures that
> +running or using those binaries will not result in a ``file not found''
> +error at run time.  @xref{Options, @option{-rpath},, ld, The GNU
> +Linker}, for more information on @code{RUNPATH}.
> +
> +@item #:substitutable?
> +This Boolean, @code{#t} by default, tells whether the package outputs

Likewise (miscapitalised).

> +should be substitutable---i.e., whether users should be able to obtain
> +substitutes for them instead of building locally (@pxref{Substitutes}).
> +
> +@item #:allowed-references
> +@itemx #:disallowed-references
> +When true, these arguments must be a list of dependencies that must not
> +appear among the references of the build results.  If, upon build
> +completion, some of these references are retained, the build process
> +fails.
> +
> +This is useful to ensure that a package does not erroneously keep a
> +reference to some of it build-time inputs, in cases where doing so
> +would, for example, unnecessarily increase its size (@pxref{Invoking
> +guix size}).
> +@end table
> +
> +Most other build systems support these keyword arguments.
>  @end defvr
>  
>  Other @code{<build-system>} objects are defined to support other

No other remarks. LGTM

Greetings,
Maxime.