Clean up a few things with the way we use rules_rust

After using rules_rust a bit more, I noticed that some of the ways we
had it set up aren't quite correct. In particular, arch-related `cfg`
didn't work for armv7, which breaks many more complex crates.

Change-Id: I5a15160abfd9da7609f7e9e4b60ec40cbe055d25
Signed-off-by: Brian Silverman <bsilver16384@gmail.com>
diff --git a/build_tests/BUILD b/build_tests/BUILD
index 705c4ff..29a1275 100644
--- a/build_tests/BUILD
+++ b/build_tests/BUILD
@@ -146,9 +146,8 @@
 
 rust_test(
     name = "hello_lib_test",
-    srcs = ["hello_lib.rs"],
+    crate = ":hello_lib",
     target_compatible_with = ["@platforms//os:linux"],
-    deps = [":hello_lib"],
 )
 
 rust_binary(