gnu: glibc: Work around broken GNU Mach header detection.

* gnu/packages/base.scm (%glibc/hurd-configure-flags): New variable.
(glibc)[arguments]: Use it.
(glibc/hurd-headers)[arguments]: likewise.
* gnu/packages/cross-base.scm (cross-libc*): Likewise.

Co-authored-by: Josselin Poiret <dev@jpoiret.xyz>

gnu/packages/base.scm

@@ -755,6 +755,17 @@ the store.")
     (home-page "https://www.gnu.org/software/guix//")
     (license gpl3+)))
 
+(define-public %glibc/hurd-configure-flags
+  ;; 'configure' in glibc 2.35 omits to pass '-ffreestanding' when detecting
+  ;; Mach headers.  This is fixed in glibc commits
+  ;; 8b8c768e3c701ed1993789bb46acb8a12c7a93df and
+  ;; 7685630b98ca2a3f5de86eadf130993e6cf998a0; as a workaround, bypass those
+  ;; tests.
+  '("ac_cv_header_mach_mach_types_defs=yes"
+    "ac_cv_header_mach_mach_types_h=yes"
+    "ac_cv_header_mach_machine_ndr_def_h=no"
+    "libc_cv_mach_task_creation_time=yes"))
+
 (define-public glibc
   ;; This is the GNU C Library, used on GNU/Linux and GNU/Hurd.  Prior to
   ;; version 2.28, GNU/Hurd used a different glibc branch.
@@ -854,7 +865,8 @@ the store.")
             ;; On GNU/Hurd we get discarded-qualifiers warnings for
             ;; 'device_write_inband' among other things.  Ignore them.
             ,@(if (hurd-target?)
-                  '("--disable-werror")
+                  `("--disable-werror"
+                    ,@%glibc/hurd-configure-flags)
                   '()))
 
       #:tests? #f                                 ; XXX
@@ -1392,9 +1404,10 @@ command.")
     (arguments
      (substitute-keyword-arguments (package-arguments glibc)
        ;; We just pass the flags really needed to build the headers.
-       ((#:configure-flags _)
+       ((#:configure-flags flags)
         `(list "--enable-add-ons"
-               "--host=i586-pc-gnu"))
+               "--host=i586-pc-gnu"
+               ,@%glibc/hurd-configure-flags))
        ((#:phases _)
         '(modify-phases %standard-phases
            (replace 'install

gnu/packages/cross-base.scm

@@ -577,7 +577,9 @@ and the cross tool chain."
            ((#:configure-flags flags)
             `(cons ,(string-append "--host=" target)
                    ,(if (target-hurd? target)
-                        `(cons "--disable-werror" ,flags)
+                        `(append (list "--disable-werror"
+                                       ,@%glibc/hurd-configure-flags)
+                                 ,flags)
                         flags)))
            ((#:phases phases)
             `(modify-phases ,phases