builder: Make xzcat binary configurable and use AC_PATH_PROG.

builder/builder.ml

@@ -301,13 +301,18 @@ let main () =
 
       output, Some size, format, delete_output_file, do_resize, true in
 
+  (* Create xzcat command to uncompress from input to output. *)
+  let xzcat_command input output =
+    sprintf "%s %s > %s" Config.xzcat input output
+  in
+
   if not do_resize then (
     (* If the user did not specify --size and the output is a regular
      * file and the format is raw, then we just uncompress the template
      * directly to the output file.  This is fast but less flexible.
      *)
     let { Index_parser.file_uri = file_uri } = entry in
-    let cmd = sprintf "xzcat %s > %s" (quote template) (quote output) in
+    let cmd = xzcat_command template output in
     if debug then eprintf "%s\n%!" cmd;
     msg (f_"Uncompressing: %s") file_uri;
     let r = Sys.command cmd in
@@ -323,7 +328,7 @@ let main () =
       (* Uncompress it to a temporary file. *)
       let { Index_parser.file_uri = file_uri } = entry in
       let tmpfile = Filename.temp_file "vbsrc" ".img" in
-      let cmd = sprintf "xzcat %s > %s" (quote template) (quote tmpfile) in
+      let cmd = xzcat_command template tmpfile in
       if debug then eprintf "%s\n%!" cmd;
       msg (f_"Uncompressing: %s") file_uri;
       let r = Sys.command cmd in

configure.ac

@@ -698,6 +698,10 @@ if test "x$WRESTOOL" != "xno"; then
     AC_DEFINE_UNQUOTED([WRESTOOL],["$WRESTOOL"],[Name of wrestool program.])
 fi
 
+dnl Check for xzcat (required).
+AC_PATH_PROGS([XZCAT],[xzcat],[no])
+test "x$XZCAT" = "xno" && AC_MSG_ERROR([xzcat must be installed])
+
 dnl Check for QEMU for running binaries on this $host_cpu, fall
 dnl back to basic 'qemu'.  Allow the user to override it.
 qemu_system="$(

mllib/config.ml.in

@@ -18,3 +18,5 @@
 
 let package_name = "@PACKAGE_NAME@"
 let package_version = "@PACKAGE_VERSION@"
+
+let xzcat = "@XZCAT@"