Update the libm submodule

This requires privately reexporting `libm`'s `support` module at crate
root, where it is expected for macros. Once `libm` is made always
available, the reexport can be simplified.

src/lib.rs

@@ -58,6 +58,20 @@ pub mod int;
     all(target_family = "wasm", not(target_os = "unknown"))
 )))]
 pub mod math;
+
+// `libm` expects its `support` module to be available in the crate root. This config can be
+// cleaned up once `libm` is made always available.
+#[cfg(not(any(
+    all(
+        target_arch = "x86",
+        not(target_feature = "sse2"),
+        not(target_os = "uefi"),
+    ),
+    unix,
+    all(target_family = "wasm", not(target_os = "unknown"))
+)))]
+use math::libm::support;
+
 pub mod mem;
 
 #[cfg(target_arch = "arm")]

src/math.rs

@@ -3,7 +3,7 @@
 #[allow(unused_imports)]
 #[allow(clippy::all)]
 #[path = "../libm/src/math/mod.rs"]
-mod libm;
+pub(crate) mod libm;
 
 #[allow(unused_macros)]
 macro_rules! no_mangle {