Prevent useless run of po/configure when nothing was changed.

Makefile.am

@@ -65,8 +65,12 @@ clean-local:
 po/Makefile: $(srcdir_po)/Makefile.in.in $(srcdir_po)/Makevars $(srcdir_po)/POTFILES.in po/config.status
 	@$(am__cd) po && @SHELL@ ./config.status ./Makefile.in po-directories
 
-# Regenerate po/config.status if this Makefile is changed as configure parameters may be updated
-po/config.status: $(srcdir_po)/configure Makefile
+po/configargs.stamp:
+	@$(MAKE) $(AM_MAKEFLAGS) $(top_builddir)/config.status && \
+	  @SHELL@ ./config.status po/configargs.stamp
+
+# Regenerate po/config.status if 'po/configure' was updated or 'configure' parameters was changed
+po/config.status: $(srcdir_po)/configure po/configargs.stamp
 	@$(MKDIR_P) po && $(am__cd) po && echo "cd po && @SHELL@ ./configure @ac_configure_args@" && \
 	  @SHELL@ $(abs_top_srcdir)/po/configure @ac_configure_args@ --srcdir=$(abs_top_srcdir)/po \
 	    --disable-option-checking --no-create --no-recursion

configure.ac

@@ -1726,8 +1726,7 @@ AC_SUBST(LDFLAGS)
 AC_SUBST([ac_configure_args])
 AC_SUBST([EMPTY_VAR], [[]])
 
-AC_CONFIG_FILES([
-libmicrohttpd.pc
+AC_CONFIG_FILES([libmicrohttpd.pc
 w32/common/microhttpd_dll_res_vc.rc
 po/configure.acT:po/configure.ac.in
 Makefile
@@ -1743,6 +1742,17 @@ src/examples/Makefile
 src/testcurl/Makefile
 src/testcurl/https/Makefile
 src/testzzuf/Makefile])
+AC_CONFIG_COMMANDS([po/configargs.stamp], [
+  $as_echo "$ac_configure_args" > "$ac_tmp/configargs.stamp" || AC_MSG_ERROR([[cannot create file $ac_tmp/configargs.stamp]])
+  AS_IF([[cmp -s "po/configargs.stamp" "$ac_tmp/configargs.stamp" >/dev/null 2>&1]],
+    [AC_MSG_NOTICE([[po/configargs.stamp is unchanged]])],
+    [
+      rm -f po/configargs.stamp
+      mv "$ac_tmp/configargs.stamp" po/configargs.stamp || AC_MSG_ERROR([[cannot create file $ac_tmp/configargs.stamp]])
+      AC_MSG_NOTICE([[po/configargs.stamp is updated]])
+    ]
+  )
+], [ac_configure_args="$ac_configure_args"])
 AC_OUTPUT
 
 # Finally: summary