Build RiveSharp with clang

We may want to try and standardize on clang SIMD vector extensions,
which means everything has to build with clang.

Diffs=
07186fc98 Build RiveSharp with clang (#4194)

.rive_head

diff --git a/.rive_head b/.rive_head
index b4cd9d5..9e28b1a 100644
--- a/.rive_head
+++ b/.rive_head
@@ -1 +1 @@
-59ecc6712369bd7c160c35bbb263a36771155923
+07186fc98800540f1723705547c9c8ef6f76044f

include/rive/math/contour_measure.hpp

diff --git a/include/rive/math/contour_measure.hpp b/include/rive/math/contour_measure.hpp
index d9be887..0965645 100644
--- a/include/rive/math/contour_measure.hpp
+++ b/include/rive/math/contour_measure.hpp
@@ -15,7 +15,7 @@
 class ContourMeasure : public RefCnt {
 public:
     static constexpr unsigned kMaxDot30 = (1 << 30) - 1;
-    static constexpr float kInvScaleD30 = 1.0f / kMaxDot30;
+    static constexpr float kInvScaleD30 = 1.0f / (float)kMaxDot30;
 
     // Deliberately making this pack well (12 bytes)
     struct Segment {