[libgda] Update README to resolve reference to non-existing INSTALL

[Vivien Malerba <vivien src gnome org>]

commit b49c649fbfed9fd4661a23c9c2f9da7e202eaf94
Author: unknown <epolger HU00104914 ericsson se>
Date:   Fri Sep 4 15:18:37 2015 +0200

    Update README to resolve reference to non-existing INSTALL

 README |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/README b/README
index 4497be6..34d082a 100644
--- a/README
+++ b/README
@@ -59,6 +59,9 @@ Further information
 libgda comes with a automatic installation tool. For a guide on how to
 install libgda, see the file named INSTALL.
 
+Please note that if you use the Git repository the INSTALL file doesn't exist
+before you run the autogen.sh script.
+
 For errors you find in the code or the documentation, please contact
 gnome-db-list gnome org or the author of the file.