* configure.ac: Create a cache file for libexec.

configure.ac

@@ -197,11 +197,16 @@ AS_IF([test "$XCONFIGURE" = "android"],[
 
   AC_MSG_NOTICE([configuring in `exec'])
 
+  # Derive a name for a cache file for this configure script from the
+  # current, if specified.
+  exec_cache_file=
+  AS_IF([test -n "$cache_file"],
+    [exec_cache_file="--cache-file=$cache_file.2"])
   OLDCWD=`pwd`
   cd exec
   $CONFIG_SHELL $emacs_srcdir/exec/configure		\
 		--host=$host "CC=$CC" "LD=$CC" "AS=$CC"	\
-		"AR=$AR" "CFLAGS=$CFLAGS"
+		"AR=$AR" "CFLAGS=$CFLAGS" $exec_cache_file
   emacs_val=$?
   cd $OLDCWD