Add basic integration test for checksum-hash-algorithm feature

tests/run-make/checksum-freshness/expected.d

@@ -0,0 +1,3 @@
+lib.d: lib.rs # checksum:blake3=5fd6328c93a3360bc580567aec10731ab3e5efc4a0f957b1bba0db0d27af3767 file_len:110
+
+lib.rs:

tests/run-make/checksum-freshness/lib.rs

@@ -0,0 +1,5 @@
+// A basic library to be used in tests with no real purpose.
+
+pub fn sum(a: i32, b: i32) -> i32 {
+    a + b
+}

tests/run-make/checksum-freshness/rmake.rs

@@ -0,0 +1,9 @@
+use run_make_support::{rfs, rustc};
+
+fn main() {
+    rustc().input("lib.rs").arg("-Zchecksum-hash-algorithm=blake3").emit("dep-info").run();
+    let make_file_contents = rfs::read_to_string("lib.d");
+    let expected_contents = rfs::read_to_string("expected.d");
+    assert_eq!(make_file_contents, expected_contents);
+    assert!(!expected_contents.is_empty());
+}