Add rerun_except to root crate

Cargo is finding more reasons to do unnecessary rebuilds, so I've added
the rerun_except crate to its build.rs as well to ignore .asm files
before recompiling.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

build.rs

@@ -0,0 +1,7 @@
+use rerun_except::rerun_except;
+
+fn main() {
+    rerun_except(&[
+        "*.asm",
+    ]).unwrap();
+}