[gegl] configure: do not allow --enable-docs in cross-compilation environment.

[Øyvind Kolås <ok src gnome org>]

commit 88036c8782d0d1e249aaaae2a5e1e4648877de89
Author: Jehan <jehan girinstud io>
Date:   Thu Jul 24 14:21:04 2014 +0000

    configure: do not allow --enable-docs in cross-compilation environment.
    
    Docs require the native compilation of tools used during later steps of
    compilation (not for the target platform). This could be later fixed to
    work properly. But in the meantime, let's just prevent people to start
    a build which will fail by design.

 configure.ac |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index d61d666..9a8be53 100644
--- a/configure.ac
+++ b/configure.ac
@@ -245,6 +245,14 @@ AC_ARG_ENABLE([docs],
               [  --disable-docs          disable docs generation (default=no)],,
               enable_docs="yes")
 
+# While cross-compiling, doc generation will fail.
+if test "$cross_compiling" = "yes" && test "x$enable_docs" = "xyes"; then
+    AC_MSG_WARN([
+*** Our build system does not support doc generation in a cross-compiled environment yet.
+Disabling doc generation.])
+    enable_docs="no (cross-compilation environment)"
+fi
+
 AM_CONDITIONAL(ENABLE_DOCS, test "x$enable_docs" = "xyes")