[ios] Fix type narrowing issue with MGLOpenGLStyleLayer projection matrix (#11664)

`CATransform3D`'s matrix is internally typed as `CGFloat`, which we were implicitly casting to from `double`.... except that the `-Wc++11-narrowing` flag disallows implicit narrowing casts and we need `double` precision, anyway.

* [ios, macos] Use MGLMatrix4 a 4x4 double matrix for MGLOpenGLStyleLayer projection matrix.

* [ios, macos] Don't use union for MGLMatrix4

1 files changed, 11 insertions, 0 deletions

diff --git a/platform/darwin/src/MGLGeometry.mm b/platform/darwin/src/MGLGeometry.mm
index 0b044f7521..6785779570 100644
--- a/platform/darwin/src/MGLGeometry.mm
+++ b/platform/darwin/src/MGLGeometry.mm
@@ -111,3 +111,14 @@ MGLMapPoint MGLMapPointForCoordinate(CLLocationCoordinate2D coordinate, double z
     mbgl::Point<double> projectedCoordinate = mbgl::Projection::project(MGLLatLngFromLocationCoordinate2D(coordinate), std::pow(2.0, zoomLevel));
     return MGLMapPointMake(projectedCoordinate.x, projectedCoordinate.y, zoomLevel);
 }
+
+MGLMatrix4 MGLMatrix4Make(std::array<double, 16>  array) {
+    MGLMatrix4 mat4 = {
+        .m00 = array[0], .m01 = array[1], .m02 = array[2], .m03 = array[3],
+        .m10 = array[4], .m11 = array[5], .m12 = array[6], .m13 = array[7],
+        .m20 = array[8], .m21 = array[9], .m22 = array[10], .m23 = array[11],
+        .m30 = array[12], .m31 = array[13], .m32 = array[14], .m33 = array[15]
+    };
+    return mat4;
+}
+