Enable final SIMD spec tests for x86

Author: abrown

build.rs

@@ -202,8 +202,6 @@ fn ignore(testsuite: &str, testname: &str, strategy: &str) -> bool {
             // to be a big chunk of work to implement them all there!
             ("simd", _) if target.contains("aarch64") => return true,
 
-            ("simd", "simd_conversions") => return true, // FIXME Unsupported feature: proposed SIMD operator I32x4TruncSatF32x4S
-
             // TODO(#1886): Ignore reference types tests if this isn't x64,
             // because Cranelift only supports reference types on x64.
             ("reference_types", _) => {