maint: update to latest gnulib

Since we're about to freeze, it's time to pick up the latest
upstream gnulib.  Among other changes, gnulib now guarantees the
use of some -f flags that we were previously manually adding.

* .gnulib: Update to latest, in part for warning improvements.
* m4/virt-compile-warnings.m4 (LIBVIRT_COMPILE_WARNINGS): Drop
flags that are now guaranteed by gnulib.
* bootstrap: Resync to gnulib.
Signed-off-by: NEric Blake <eblake@redhat.com>

.gnulib @ 4a5ee89c

-Subproject commit 0ba087759d2797c8f7d3c34bef6268ba3fd212cb
+Subproject commit 4a5ee89c8a8be7350a8fd8ca1bacb196a190e492

bootstrap

@@ -209,12 +209,16 @@ bootstrap_sync=false
 # Use git to update gnulib sources
 use_git=true
 
+check_exists() {
+  ($1 --version </dev/null) >/dev/null 2>&1
+  test $? -lt 126
+}
+
 # find_tool ENVVAR NAMES...
 # -------------------------
 # Search for a required program.  Use the value of ENVVAR, if set,
-# otherwise find the first of the NAMES that can be run (i.e.,
-# supports --version).  If found, set ENVVAR to the program name,
-# die otherwise.
+# otherwise find the first of the NAMES that can be run.
+# If found, set ENVVAR to the program name, die otherwise.
 #
 # FIXME: code duplication, see also gnu-web-doc-update.
 find_tool ()
@@ -225,7 +229,7 @@ find_tool ()
   eval "find_tool_res=\$$find_tool_envvar"
   if test x"$find_tool_res" = x; then
     for i; do
-      if ($i --version </dev/null) >/dev/null 2>&1; then
+      if check_exists $i; then
         find_tool_res=$i
         break
       fi
@@ -463,8 +467,7 @@ check_versions() {
     if [ "$req_ver" = "-" ]; then
       # Merely require app to exist; not all prereq apps are well-behaved
       # so we have to rely on $? rather than get_version.
-      $app --version >/dev/null 2>&1 </dev/null
-      if [ 126 -le $? ]; then
+      if ! check_exists $app; then
         warn_ "Error: '$app' not found"
         ret=1
       fi
@@ -551,10 +554,10 @@ fi
 echo "$0: Bootstrapping from checked-out $package sources..."
 
 # See if we can use gnulib's git-merge-changelog merge driver.
-if $use_git && test -d .git && (git --version) >/dev/null 2>/dev/null ; then
+if $use_git && test -d .git && check_exists git; then
   if git config merge.merge-changelog.driver >/dev/null ; then
     :
-  elif (git-merge-changelog --version) >/dev/null 2>/dev/null ; then
+  elif check_exists git-merge-changelog; then
     echo "$0: initializing git-merge-changelog driver"
     git config merge.merge-changelog.name 'GNU-style ChangeLog merge driver'
     git config merge.merge-changelog.driver 'git-merge-changelog %O %A %B'

m4/virt-compile-warnings.m4

@@ -187,8 +187,6 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[
     esac
     wantwarn="$wantwarn -fexceptions"
     wantwarn="$wantwarn -fasynchronous-unwind-tables"
-    wantwarn="$wantwarn -fdiagnostics-show-option"
-    wantwarn="$wantwarn -funit-at-a-time"
 
     # Need -fipa-pure-const in order to make -Wsuggest-attribute=pure
     # fire even without -O.