[gnome-builder] build: add some new GCC warnings

[Christian Hergert <chergert src gnome org>]

commit 6ab0a16a6b2ce81ded0c7188a1748b6c65a5d838
Author: Christian Hergert <christian hergert me>
Date:   Mon May 18 13:03:23 2015 -0700

    build: add some new GCC warnings

 configure.ac |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 296e35f..a84d297 100644
--- a/configure.ac
+++ b/configure.ac
@@ -225,7 +225,9 @@ AX_APPEND_COMPILE_FLAGS([ \
        -Wformat-nonliteral \
        -Wformat-security \
        -Winit-self \
+       -Wmisleading-indentation \
        -Wmissing-include-dirs \
+       -Wshift-negative-value \
        -Wnested-externs \
        -Wno-missing-field-initializers \
        -Wno-sign-compare \