ANGLE: fix DllMain collision in static builds

The symbol is simply renamed in static builds, allowing wrappers of the
library to still call the function if needed.

Task-number: QTBUG-46209
Change-Id: I5d4ad2df59f206a3794b99364d122f9d0f12f8c6
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Tim Blechmann <tim@klingt.org>
Reviewed-by: Kai Koehne <kai.koehne@theqtcompany.com>

src/angle/src/libGLESv2/libGLESv2.pro

@@ -329,6 +329,8 @@ angle_d3d11 {
 !static {
     DEF_FILE = $$ANGLE_DIR/src/libGLESv2/$${TARGET}.def
     mingw:equals(QT_ARCH, i386): DEF_FILE = $$ANGLE_DIR/src/libGLESv2/$${TARGET}_mingw32.def
+} else {
+    DEFINES += DllMain=DllMain_ANGLE # prevent symbol from conflicting with the user's DllMain
 }
 
 float_converter.target = float_converter