I've investigated a bit more: Guix's gcc-4.7 passes
(string-append "--with-native-system-header-dir=" libc "/include")
where libc is (assoc-ref %build-inputs "libc")
.
However, further down, there is
`(let* ((libc (assoc-ref %build-inputs "libc"))
(libc-native (or (assoc-ref %build-inputs "libc-native")
libc)))
which makes me think that "--with-native-system-header-dir=" should use
libc-native if the latter is present.
It would be possible to pass "--with-headers=" to gcc which would make it copy
the specified directory into the gcc installation directory and everything
would work without weird workarounds.
The gcc option "--with-headers=" is deprecated in favor of "--with-sysroot".
Also, the gcc manual says:
> "If the specified directory is a subdirectory of ${exec_prefix}, then it will
> be found relative to the GCC binaries if the installation tree is moved."
Not sure we want that.
The gcc manual says:
>If you specify the --with-native-system-header-dir=dirname option then the
>compiler will search that directory within dirname for native system headers
>rather than the default /usr/include.
So I guess a quick workaround would be to specify "--with-headers=" libc for
cross-gcc. That would make the resulting gcc much larger since it would copy
glibc into it.
The right fix would be to specify "--with-sysroot=" or to use our patch.
In any case, what guix master does with
(string-append "--with-native-system-header-dir=" libc "/include")
where libc is (assoc-ref %build-inputs "libc")
is seriously bad. Should replace that by (or libc-native libc) in that order.
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