gnu: qtbase: Restore compilation on linux kernels < 4.11.

Fixes <https://bugs.gnu.org/34431>.

* gnu/packages/patches/qtbase-old-kernel.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register patch.
* gnu/packages/qt.scm (qtbase): Add patch.

gnu/local.mk

@@ -1180,6 +1180,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/qemu-CVE-2018-16872.patch 		\
   %D%/packages/patches/qemu-CVE-2019-6778.patch 		\
   %D%/packages/patches/qt4-ldflags.patch			\
+  %D%/packages/patches/qtbase-old-kernel.patch			\
   %D%/packages/patches/qtbase-use-TZDIR.patch			\
   %D%/packages/patches/qtscript-disable-tests.patch		\
   %D%/packages/patches/quagga-reproducible-build.patch          \

gnu/packages/patches/qtbase-old-kernel.patch

@@ -0,0 +1,25 @@
+https://672856.bugs.gentoo.org/attachment.cgi?id=557978
+https://bugs.gentoo.org/672856
+
+The patch fixes building qtbase with linux kernels < 4.11.
+See bug #34431.
+
+diff -Naurp a/src/corelib/global/minimum-linux_p.h b/src/corelib/global/minimum-linux_p.h
+--- a/src/corelib/global/minimum-linux_p.h      2018-11-25 15:51:11.000000000 +0300
++++ b/src/corelib/global/minimum-linux_p.h      2018-12-17 13:25:38.176823753 +0300
+@@ -75,14 +75,9 @@ QT_BEGIN_NAMESPACE
+  * - accept4                    2.6.28
+  * - renameat2                  3.16                    QT_CONFIG(renameat2)
+  * - getrandom                  3.17                    QT_CONFIG(getentropy)
+- * - statx                      4.11                    QT_CONFIG(statx)
+  */
+
+-#if QT_CONFIG(statx)
+-#  define MINLINUX_MAJOR        4
+-#  define MINLINUX_MINOR        11
+-#  define MINLINUX_PATCH        0
+-#elif QT_CONFIG(getentropy)
++#if QT_CONFIG(getentropy)
+ #  define MINLINUX_MAJOR        3
+ #  define MINLINUX_MINOR        17
+ #  define MINLINUX_PATCH        0

gnu/packages/qt.scm

@@ -512,7 +512,8 @@ system, and the core design of Django is reused in Grantlee.")
               (base32
                "071yc9iz14qs4s8yvrwllyfdzp5yjxsdpvbjxdrf0g5q69vqigy6"))
              ;; Use TZDIR to avoid depending on package "tzdata".
-             (patches (search-patches "qtbase-use-TZDIR.patch"))
+             (patches (search-patches "qtbase-use-TZDIR.patch"
+                                      "qtbase-old-kernel.patch"))
              (modules '((guix build utils)))
              (snippet
                ;; corelib uses bundled harfbuzz, md4, md5, sha3