Fix meson.build to correctly set graphicmagick define

meson.build

@@ -7,11 +7,10 @@ sqlite_dep = dependency('sqlite3')
 magick_dep = dependency('Magick++', required : false)
 if not magick_dep.found()
 	magick_dep = dependency('GraphicsMagick++', required : false)
+	add_global_arguments('-Dgraphicsmagick', language : 'cpp')
 endif
 if not magick_dep.found()
 	error('ImageMagick++ or GraphicsMagick++ not found.')
-else
-	add_global_arguments('-Dgraphicsmagick', language : 'cpp')
 endif
 
 link = ['-lgpx', '-lheatmap']