gnu: glibc: Update to 2.27.

* gnu/packages/base.scm (glibc/linux): Update to 2.27.
[source](patches): Add 'glibc-hidden-visibility-ldconfig.patch' and
'glibc-2.27-git-fixes.patch'.
[native-inputs]: Add BISON.
[arguments]: Remove deprecated "--enable-add-ons" from #:configure-flags.
Also remove unneeded "libc_cv_ssp=no" and "libcv_ssp_strong=no".
(glibc-2.26): New public variable.
* gnu/packages/commencement.scm (glibc-final-with-bootstrap-bash)[native-inputs]:
Add BISON-BOOT0.
* gnu/packages/patches/glibc-2.27-git-fixes.patch,
gnu/packages/patches/glibc-hidden-visibility-ldconfig.patch: New files.
* gnu/local.mk (dist_patch_DATA): Register them.

gnu/packages/base.scm

@@ -36,6 +36,7 @@
   #:use-module (gnu packages)
   #:use-module (gnu packages acl)
   #:use-module (gnu packages bash)
+  #:use-module (gnu packages bison)
   #:use-module (gnu packages ed)
   #:use-module (gnu packages guile)
   #:use-module (gnu packages multiprecision)
@@ -538,26 +539,15 @@ store.")
 (define-public glibc/linux
   (package
    (name "glibc")
-   ;; Glibc has stable branches that continuously pick fixes for each supported
-   ;; release.  Unfortunately they do not do point-releases, so we are stuck
-   ;; with copying almost all patches, or use a snapshot of the release branch.
-   ;;
-   ;; This version number corresponds to the output of `git describe` and the
-   ;; archive can be generated by checking out the commit ID and running:
-   ;;  git archive --prefix=$(git describe)/ HEAD | xz > $(git describe).tar.xz
-   ;; See <https://bugs.gnu.org/29406> for details.
-   ;;
    ;; Note: Always use a dot after the minor version since various places rely
    ;; on "version-major+minor" to determine where locales are found.
-   (version "2.26.105-g0890d5379c")
+   (version "2.27")
    (source (origin
             (method url-fetch)
-            (uri (string-append "https://alpha.gnu.org/gnu/guix/mirror/"
-                                "glibc-" (version-major+minor version) "-"
-                                (caddr (string-split version #\.)) ".tar.xz"))
+            (uri (string-append "mirror://gnu/glibc/glibc-" version ".tar.xz"))
             (sha256
              (base32
-              "1jck0c1i248sn02rvsfjykk77qncma34bjq89dyy2irwm50d7s3g"))
+              "0wpwq7gsm7sd6ysidv0z575ckqdg13cr2njyfgrbgh4f65adwwji"))
             (snippet
              ;; Disable 'ldconfig' and /etc/ld.so.cache.  The latter is
              ;; required on LFS distros to avoid loading the distro's libc.so
@@ -569,6 +559,8 @@ store.")
                 #t))
             (modules '((guix build utils)))
             (patches (search-patches "glibc-ldd-x86_64.patch"
+                                     "glibc-2.27-git-fixes.patch"
+                                     "glibc-hidden-visibility-ldconfig.patch"
                                      "glibc-versioned-locpath.patch"
                                      "glibc-allow-kernel-2.6.32.patch"))))
    (build-system gnu-build-system)
@@ -595,8 +587,7 @@ store.")
                  (guix build gnu-build-system))
 
       #:configure-flags
-      (list "--enable-add-ons"
-            "--sysconfdir=/etc"
+      (list "--sysconfdir=/etc"
 
             ;; Installing a locale archive with all the locales is to
             ;; expensive (~100 MiB), so we rely on users to install the
@@ -631,10 +622,7 @@ store.")
             ;; Use our Bash instead of /bin/sh.
             (string-append "BASH_SHELL="
                            (assoc-ref %build-inputs "bash")
-                           "/bin/bash")
-
-            ;; XXX: Work around "undefined reference to `__stack_chk_guard'".
-            "libc_cv_ssp=no" "libc_cv_ssp_strong=no")
+                           "/bin/bash"))
 
       #:tests? #f                                 ; XXX
       #:phases (modify-phases %standard-phases
@@ -745,6 +733,7 @@ store.")
    ;; install the message catalogs, with 'msgfmt'.
    (native-inputs `(("texinfo" ,texinfo)
                     ("perl" ,perl)
+                    ("bison" ,bison)
                     ("gettext" ,gettext-minimal)))
 
    (native-search-paths
@@ -853,6 +842,26 @@ GLIBC/HURD for a Hurd host"
 ;; Below are old libc versions, which we use mostly to build locale data in
 ;; the old format (which the new libc cannot cope with.)
 
+(define-public glibc-2.26
+  (package
+    (inherit glibc)
+    ;; This version number corresponds to the output of `git describe` and the
+    ;; archive can be generated by checking out the commit ID and running:
+    ;;  git archive --prefix=$(git describe)/ HEAD | xz > $(git describe).tar.xz
+    ;; See <https://bugs.gnu.org/29406> for why this was necessary.
+    (version "2.26.105-g0890d5379c")
+    (source (origin
+              (inherit (package-source glibc))
+              (uri (string-append "https://alpha.gnu.org/gnu/guix/mirror/"
+                                  "glibc-" (version-major+minor version) "-"
+                                  (caddr (string-split version #\.)) ".tar.xz"))
+              (sha256
+               (base32
+                "1jck0c1i248sn02rvsfjykk77qncma34bjq89dyy2irwm50d7s3g"))
+              (patches (search-patches "glibc-ldd-x86_64.patch"
+                                       "glibc-versioned-locpath.patch"
+                                       "glibc-allow-kernel-2.6.32.patch"))))))
+
 (define-public glibc-2.25
   (package
     (inherit glibc)