config: Add check whether D compiler works (PR103528)

As well as checking for the existence of a GDC compiler, also validate
that it has also been built with libphobos, otherwise warn or fail with
the message that GDC is required to build d.

config/ChangeLog:

	PR d/103528
	* acx.m4 (ACX_PROG_GDC): Add check whether D compiler works.

ChangeLog:

	* configure: Regenerate.

config/acx.m4

@@ -425,7 +425,20 @@ AC_DEFUN([ACX_PROG_GDC],
 [AC_REQUIRE([AC_CHECK_TOOL_PREFIX])
 AC_REQUIRE([AC_PROG_CC])
 AC_CHECK_TOOL(GDC, gdc, no)
+AC_CACHE_CHECK([whether the D compiler works],
+		 acx_cv_d_compiler_works,
+[cat >conftest.d <<EOF
+module conftest; int main() { return 0; }
+EOF
+acx_cv_d_compiler_works=no
 if test "x$GDC" != xno; then
+  errors=`(${GDC} $1[]m4_ifval([$1], [ ])-c conftest.d) 2>&1 || echo failure`
+  if test x"$errors" = x && test -f conftest.$ac_objext; then
+    acx_cv_d_compiler_works=yes
+  fi
+  rm -f conftest.*
+fi])
+if test "x$GDC" != xno && test x$acx_cv_d_compiler_works != xno; then
   have_gdc=yes
 else
   have_gdc=no

configure

@@ -5727,7 +5727,26 @@ else
   GDC="$ac_cv_prog_GDC"
 fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether the D compiler works" >&5
+$as_echo_n "checking whether the D compiler works... " >&6; }
+if ${acx_cv_d_compiler_works+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat >conftest.d <<EOF
+module conftest; int main() { return 0; }
+EOF
+acx_cv_d_compiler_works=no
 if test "x$GDC" != xno; then
+  errors=`(${GDC} -c conftest.d) 2>&1 || echo failure`
+  if test x"$errors" = x && test -f conftest.$ac_objext; then
+    acx_cv_d_compiler_works=yes
+  fi
+  rm -f conftest.*
+fi
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $acx_cv_d_compiler_works" >&5
+$as_echo "$acx_cv_d_compiler_works" >&6; }
+if test "x$GDC" != xno && test x$acx_cv_d_compiler_works != xno; then
   have_gdc=yes
 else
   have_gdc=no