Make Mat2D constructors constexpr

Diffs=
33aec1b20 Make Mat2D constructors constexpr (#5932)

Co-authored-by: Chris Dalton <99840794+csmartdalton@users.noreply.github.com>

.rive_head

diff --git a/.rive_head b/.rive_head
index 902ce9d..6b700cd 100644
--- a/.rive_head
+++ b/.rive_head
@@ -1 +1 @@
-4335a2cd2f18b8f8cb30555ff5a6fa24a1d54143
+33aec1b20028fed8d1cf790378db26241212784f

include/rive/math/mat2d.hpp

diff --git a/include/rive/math/mat2d.hpp b/include/rive/math/mat2d.hpp
index 08360ed..6c347c6 100644
--- a/include/rive/math/mat2d.hpp
+++ b/include/rive/math/mat2d.hpp
@@ -11,8 +11,8 @@
 class Mat2D
 {
 public:
-    Mat2D() : m_buffer{{1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f}} {}
-    Mat2D(float x1, float y1, float x2, float y2, float tx, float ty) :
+    constexpr Mat2D() : m_buffer{{1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f}} {}
+    constexpr Mat2D(float x1, float y1, float x2, float y2, float tx, float ty) :
         m_buffer{{x1, y1, x2, y2, tx, ty}}
     {}
 

src/shapes/path_composer.cpp

diff --git a/src/shapes/path_composer.cpp b/src/shapes/path_composer.cpp
index 096848c..34faf3d 100644
--- a/src/shapes/path_composer.cpp
+++ b/src/shapes/path_composer.cpp
@@ -6,8 +6,6 @@
 
 using namespace rive;
 
-static Mat2D identity;
-
 PathComposer::PathComposer(Shape* shape) : m_Shape(shape), m_deferredPathDirt(false) {}
 
 void PathComposer::buildDependencies()