[folks] build: Mark as not supporting srcdir != builddir

[Philip Withnall <pwithnall src gnome org>]

commit 69030c4037fe02d98d1dafc330a3c556c6653814
Author: Colin Walters <walters verbum org>
Date:   Fri Jan 23 14:31:17 2015 +0000

    build: Mark as not supporting srcdir != builddir
    
    Basically automake's vala rules cd $(srcdir), which breaks variable
    references like $(top_srcdir), since they're relative to the build
    directory.

 configure.ac |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 79f72dd..cc44861 100644
--- a/configure.ac
+++ b/configure.ac
@@ -381,6 +381,12 @@ AC_ARG_ENABLE([vala],
               [enable_vala=$enableval],
               [enable_vala=no])
 
+# http://people.gnome.org/~walters/docs/build-api.txt
+# We don't support separate builddir when building from git;
+# The automake vala rules run cd srcdir which screws up the
+# top_srcdir variable references.
+echo \#buildapi-variable-no-builddir >/dev/null
+
 # will be re-set as necessary below
 AM_CONDITIONAL([HAVE_INTROSPECTION], [test "x$enable_vala" = "xyes"])
 sd=${srcdir}/