[gnome-photos/wip/rishi/define-m-pi] utils: Avoid a potential build failure due to undefined M_PI constant

[Debarshi Ray <debarshir src gnome org>]

commit 7903bcbda8b409e96f2a5cebae2799267a83d012
Author: Sam Thursfield <sam afuera me uk>
Date:   Wed May 27 13:07:58 2020 +0200

    utils: Avoid a potential build failure due to undefined M_PI constant
    
    The <math.h> header needs to be included.
    
    Previously I suppose libtracker-sparql.h pulled this in.

 src/photos-utils.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/photos-utils.c b/src/photos-utils.c
index 401f52ba..21bf4e20 100644
--- a/src/photos-utils.c
+++ b/src/photos-utils.c
@@ -26,6 +26,8 @@
 
 #include "config.h"
 
+#include <math.h>
+
 #include <gdk/gdk.h>
 #include <glib.h>
 #include <tracker-sparql.h>