configure: for cross, a matching ocamlrun must be on the system.

(Patch by Adrien Nader!)

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13852 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02

INSTALL

@@ -76,6 +76,15 @@ The "configure" script accepts the following options:
         hand. The installation instructions for gcc or emacs contain a
         complete list of configuration names.
 
+-target <targettype>            (default: same as -host)
+        The type of the target machine, in GNU's "configuration name"
+        format (CPU-COMPANY-SYSTEM or CPU-COMPANY-KERNEL-SYSTEM).
+        Setting this will setup OCaml as a cross-compiler which runs on
+        $host and produces code for $target. This requires a C toolchain
+        which also produces code for $target and a native OCaml
+        compiler of the exact same version (if you want a cross 4.00.1,
+        you need a native 4.00.1).
+
 -x11include <include_dir>       (default: determined automatically)
 -x11lib     <lib_dir>           (default: determined automatically)
         Location of the X11 include directory (e.g. /usr/X11R6/include)

configure

@@ -390,6 +390,30 @@ case $? in
          "Make sure the C compiler $cc is properly installed.";;
 esac
 
+# Determine which ocamlrun executable to use; for cross-compilation, a native
+# "ocamlrun" executable must be available on the system.
+if test x"$target" != x"$host"; then
+  if ! sh ./searchpath ocamlrun; then
+    err "Cross-compilation requires an ocaml runtime environment\n" \
+        "(the ocamlrun binary). Moreover, its version must be the same\n" \
+        "as the one you're trying to build (`cut -f1 -d+ < ../../VERSION`)."
+  else
+    ocaml_system_version=`ocamlrun -version | sed 's/[^0-9]*\([0-9.]\+\).*/\1/'`
+    ocaml_source_version=`sed -n '1 s/\([0-9\.]\+\).*/\1/ p' < ../../VERSION`
+    if test x"$ocaml_system_version" != x"$ocaml_source_version"; then
+      err "While you have an ocaml runtime environment, its version\n" \
+          "($ocaml_system_version) doesn't match the version of these sources\n" \
+          "($ocaml_source_version)."
+    else
+      CAMLRUN="ocamlrun"
+    fi
+  fi
+else
+  CAMLRUN=`cd ../.. && pwd`/boot/ocamlrun
+fi
+
+echo "CAMLRUN=$CAMLRUN" >> Makefile
+
 # Check the sizes of data types
 
 inf "Checking the sizes of integers and pointers..."