Fix clippy complaints in build.rs

Clippy doesn't like `if !thing.ok() { panic!(msg) }`.
Clippy prefers `assert!(thing_ok(), msg)`.
Ok, clippy.

Signed-off-by: Will Woods <[email protected]>

build.rs

@@ -77,9 +77,7 @@ fn build_rs_tests(in_path: &Path, out_path: &Path) {
             .status()
             .unwrap_or_else(|_| panic!("failed to compile {:#?}", &in_source));
 
-        if !status.success() {
-            panic!("Failed to compile {:?}", &in_source);
-        }
+        assert!(status.success(), "Failed to compile {:?}", &in_source);
     }
 }
 
@@ -105,9 +103,7 @@ fn build_cc_tests(in_path: &Path, out_path: &Path) {
             .status()
             .unwrap_or_else(|_| panic!("failed to compile {:#?}", &in_source));
 
-        if !status.success() {
-            panic!("Failed to compile {:?}", &in_source);
-        }
+        assert!(status.success(), "Failed to compile {:?}", &in_source);
     }
 }