Exclude expansion tests from test suite by default

This test isn't high enough signal to have all contributors run it.

.github/workflows/ci.yml

@@ -60,18 +60,6 @@ jobs:
       - run: cd test_suite/no_std && cargo build
         if: matrix.os != 'windows'
 
-  macro:
-    name: Macro test
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v2
-      - uses: dtolnay/rust-toolchain@nightly
-      - name: Download cargo-expand
-        run: |
-          curl -sSo ~/.cargo/bin/cargo-expand https://github.com/dtolnay/cargo-expand/releases/download/0.6.0/cargo-expand
-          chmod +x ~/.cargo/bin/cargo-expand
-      - run: cd test_suite && cargo test --test expandtest
-
   msrv:
     name: Rust 1.13.0
     runs-on: ubuntu-latest

test_suite/Cargo.toml

@@ -7,6 +7,7 @@ publish = false
 build = "build.rs"
 
 [features]
+expandtest = []
 unstable = ["serde/unstable"]
 
 [dependencies]

test_suite/build.rs

@@ -23,7 +23,7 @@ fn has_rustfmt() -> bool {
 }
 
 fn main() {
-    if has_cargo_expand() && has_rustfmt() {
+    if cfg!(feature = "expandtest") && has_cargo_expand() && has_rustfmt() {
         println!("cargo:rustc-cfg=expandtest");
     }
 }