Fix build on FreeBSD

src/plugins/platforms/wayland/egl_wayland_backend.cpp

@@ -36,6 +36,8 @@
 #include <QFile>
 #include <QOpenGLContext>
 
+#include <cmath>
+
 namespace KWin
 {
 namespace Wayland

src/plugins/platforms/wayland/wayland_backend.cpp

@@ -58,6 +58,8 @@
 #include <unistd.h>
 #include <fcntl.h>
 
+#include <cmath>
+
 namespace KWin
 {
 namespace Wayland