[gnome-packagekit] trivial: Actually apply the warning flags

[Richard Hughes <rhughes src gnome org>]

commit a29422f344ee765f11386890a083e2196a8c4065
Author: Richard Hughes <richard hughsie com>
Date:   Sat Aug 27 08:28:52 2016 +0100

    trivial: Actually apply the warning flags

 configure.ac |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 885e8e6..488ec37 100644
--- a/configure.ac
+++ b/configure.ac
@@ -65,6 +65,7 @@ WARN_CFLAGS_EXTRA="
        -Wunused-but-set-variable
        -Wwrite-strings"
 AX_APPEND_COMPILE_FLAGS([$WARN_CFLAGS_EXTRA], [WARN_CFLAGS])
+AC_SUBST(WARN_CFLAGS)
 
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