Avoid pulling in X11 headers in brcm backend

In some configurations we may end up using Mesa's EGL headers instead
of the Broadcom ones. Make this work by setting the usual define to
prevent including Xlib headers that then conflict with all sorts of
things in QtCore.

Change-Id: I4970553428e5b0e81bd76694980f3b6b194ae4c2
Reviewed-by: Andy Nichols <andy.nichols@theqtcompany.com>

src/plugins/platforms/eglfs/deviceintegration/eglfs_brcm/eglfs_brcm.pro

@@ -12,6 +12,9 @@ CONFIG += egl
 LIBS += -lbcm_host
 QMAKE_LFLAGS += $$QMAKE_LFLAGS_NOUNDEF
 
+# Avoid X11 header collision
+DEFINES += MESA_EGL_NO_X11_HEADERS
+
 SOURCES += $$PWD/qeglfsbrcmmain.cpp \
            $$PWD/qeglfsbrcmintegration.cpp