Move rustc_mir::transform to rustc_mir_transform.

compiler/rustc_mir_transform/src/coverage/test_macros/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "coverage_test_macros"
+version = "0.0.0"
+edition = "2018"
+
+[lib]
+proc-macro = true
+doctest = false

compiler/rustc_mir_transform/src/coverage/test_macros/src/lib.rs

@@ -0,0 +1,6 @@
+use proc_macro::TokenStream;
+
+#[proc_macro]
+pub fn let_bcb(item: TokenStream) -> TokenStream {
+    format!("let bcb{} = graph::BasicCoverageBlock::from_usize({});", item, item).parse().unwrap()
+}