glib: patch for rhel6, centos6, and sl6 (#8947)

var/spack/repos/builtin/packages/glib/old-kernels.patch

@@ -0,0 +1,16 @@
+--- a/gio/gfile.c     2018-06-11 15:28:30.527667202 -0500
++++ b/gio/gfile.c     2018-03-12 11:23:37.000000000 -0500
+@@ -3014,11 +3014,11 @@
+ 
+   /* Try a 1MiB buffer for improved throughput. If that fails, use the default
+    * pipe size. See: https://bugzilla.gnome.org/791457 */
+-  buffer_size = fcntl (buffer[1], F_SETPIPE_SZ, 1024 * 1024);
++  buffer_size = -1;
+   if (buffer_size <= 0)
+     {
+       int errsv;
+-      buffer_size = fcntl (buffer[1], F_GETPIPE_SZ);
++      buffer_size = 65536;
+       errsv = errno;
+ 
+       if (buffer_size <= 0)

var/spack/repos/builtin/packages/glib/package.py

@@ -72,6 +72,10 @@ class Glib(AutotoolsPackage):
     # Clang doesn't seem to acknowledge the pragma lines to disable the -Werror
     # around a legitimate usage.
     patch('no-Werror=format-security.patch')
+    # Patch to prevent compiler errors in kernels older than 2.6.35
+    patch('old-kernels.patch', when='@2.56: os=rhel6')
+    patch('old-kernels.patch', when='@2.56: os=centos6')
+    patch('old-kernels.patch', when='@2.56: os=sl6')
 
     def url_for_version(self, version):
         """Handle glib's version-based custom URLs."""