[vala/0.44] build: Require --with-cgraph configure flag when cross-compiling

[Rico Tzschichholz <ricotz src gnome org>]

commit 911973341ff70d6b6b00ce612d99e0aaf699106d
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Tue Apr 2 12:31:58 2019 +0200

    build: Require --with-cgraph configure flag when cross-compiling
    
    Fixes https://gitlab.gnome.org/GNOME/vala/issues/775

 configure.ac | 12 ++++++++++++
 1 file changed, 12 insertions(+)
---
diff --git a/configure.ac b/configure.ac
index 16ebd1f81..504db13aa 100644
--- a/configure.ac
+++ b/configure.ac
@@ -156,6 +156,7 @@ PKG_CHECK_MODULES(GMODULE, gmodule-2.0 >= $GLIB_REQUIRED)
 AC_SUBST(GMODULE_CFLAGS)
 AC_SUBST(GMODULE_LIBS)
 
+AC_ARG_WITH(cgraph, AS_HELP_STRING([--with-cgraph], [Required flag for cross-compilation to define 
capability of graphviz]), [], with_cgraph=check)
 AC_ARG_ENABLE(valadoc, AS_HELP_STRING([--disable-valadoc], [Disable valadoc]), enable_valadoc=$enableval, 
enable_valadoc=yes)
 if test x$enable_valadoc = xyes; then
        PKG_CHECK_MODULES(LIBGVC, libgvc >= $LIBGVC_REQUIRED)
@@ -181,6 +182,17 @@ if test x$enable_valadoc = xyes; then
                ], [
                        AC_MSG_RESULT([no])
                        have_cgraph=no
+               ], [
+                       if test x$with_cgraph = xcheck; then
+                               AC_MSG_ERROR([--with-cgraph=yes/no is required for cross-compilation])
+                       elif test x$with_cgraph = xyes; then
+                               AC_MSG_RESULT([yes])
+                               VALAFLAGS="$VALAFLAGS -D WITH_CGRAPH"
+                               have_cgraph=yes
+                       else
+                               AC_MSG_RESULT([no])
+                               have_cgraph=no
+                       fi
                ]
        )
        LIBADD="$cgraph_tmp_LIBADD"