build: Check for cargo when building rust language

Prevent rust language from building when cargo is
missing.

config/ChangeLog:

	* acx.m4: Add a macro to check for rust
	components.

ChangeLog:

	* configure: Regenerate.
	* configure.ac: Emit an error message when cargo
	is missing.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

config/acx.m4

@@ -424,6 +424,17 @@ else
 fi
 ])
 
+# Test for Rust
+# We require cargo and rustc for some parts of the rust compiler.
+AC_DEFUN([ACX_PROG_CARGO],
+[AC_REQUIRE([AC_CHECK_TOOL_PREFIX])
+AC_CHECK_TOOL(CARGO, cargo, no)
+if test "x$CARGO" != xno; then
+  have_cargo=yes
+else
+  have_cargo=no
+fi])
+
 # Test for D.
 AC_DEFUN([ACX_PROG_GDC],
 [AC_REQUIRE([AC_CHECK_TOOL_PREFIX])

configure

@@ -714,6 +714,7 @@ PGO_BUILD_GEN_CFLAGS
 HAVE_CXX11_FOR_BUILD
 HAVE_CXX11
 do_compare
+CARGO
 GDC
 GNATMAKE
 GNATBIND
@@ -5786,6 +5787,104 @@ else
   have_gdc=no
 fi
 
+
+if test -n "$ac_tool_prefix"; then
+  # Extract the first word of "${ac_tool_prefix}cargo", so it can be a program name with args.
+set dummy ${ac_tool_prefix}cargo; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_prog_CARGO+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$CARGO"; then
+  ac_cv_prog_CARGO="$CARGO" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_CARGO="${ac_tool_prefix}cargo"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+fi
+fi
+CARGO=$ac_cv_prog_CARGO
+if test -n "$CARGO"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $CARGO" >&5
+$as_echo "$CARGO" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+fi
+if test -z "$ac_cv_prog_CARGO"; then
+  ac_ct_CARGO=$CARGO
+  # Extract the first word of "cargo", so it can be a program name with args.
+set dummy cargo; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_prog_ac_ct_CARGO+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$ac_ct_CARGO"; then
+  ac_cv_prog_ac_ct_CARGO="$ac_ct_CARGO" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_ac_ct_CARGO="cargo"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+fi
+fi
+ac_ct_CARGO=$ac_cv_prog_ac_ct_CARGO
+if test -n "$ac_ct_CARGO"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_ct_CARGO" >&5
+$as_echo "$ac_ct_CARGO" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+  if test "x$ac_ct_CARGO" = x; then
+    CARGO="no"
+  else
+    case $cross_compiling:$ac_tool_warned in
+yes:)
+{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: using cross tools not prefixed with host triplet" >&5
+$as_echo "$as_me: WARNING: using cross tools not prefixed with host triplet" >&2;}
+ac_tool_warned=yes ;;
+esac
+    CARGO=$ac_ct_CARGO
+  fi
+else
+  CARGO="$ac_cv_prog_CARGO"
+fi
+
+if test "x$CARGO" != xno; then
+  have_cargo=yes
+else
+  have_cargo=no
+fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking how to compare bootstrapped objects" >&5
 $as_echo_n "checking how to compare bootstrapped objects... " >&6; }
 if ${gcc_cv_prog_cmp_skip+:} false; then :
@@ -9099,6 +9198,24 @@ $as_echo "$as_me: WARNING: --enable-host-shared required to build $language" >&2
           ;;
         esac
 
+        # Disable Rust if cargo is unavailable.
+        case ${add_this_lang}:${language}:${have_cargo} in
+          yes:rust:no)
+            # Specifically requested language; tell them.
+            as_fn_error $? "cargo is required to build $language" "$LINENO" 5
+            ;;
+          all:rust:no)
+            { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: cargo is required to build $language" >&5
+$as_echo "$as_me: WARNING: cargo is required to build $language" >&2;}
+            add_this_lang=unsupported
+            ;;
+          *:rust:no)
+            # Silently disable.
+            add_this_lang=unsupported
+            ;;
+        esac
+
+
         # Disable a language that is unsupported by the target.
 	case "${add_this_lang}: $unsupported_languages " in
 	  no:*) ;;

configure.ac

@@ -1411,6 +1411,7 @@ fi
 
 ACX_PROG_GNAT
 ACX_PROG_GDC
+ACX_PROG_CARGO
 ACX_PROG_CMP_IGNORE_INITIAL
 
 AC_ARG_ENABLE([bootstrap],
@@ -2305,6 +2306,23 @@ directories, to avoid imposing the performance cost of
           ;;
         esac
 
+        # Disable Rust if cargo is unavailable.
+        case ${add_this_lang}:${language}:${have_cargo} in
+          yes:rust:no)
+            # Specifically requested language; tell them.
+            AC_MSG_ERROR([cargo is required to build $language])
+            ;;
+          all:rust:no)
+            AC_MSG_WARN([cargo is required to build $language])
+            add_this_lang=unsupported
+            ;;
+          *:rust:no)
+            # Silently disable.
+            add_this_lang=unsupported
+            ;;
+        esac
+
+
         # Disable a language that is unsupported by the target.
 	case "${add_this_lang}: $unsupported_languages " in
 	  no:*) ;;