Allow a number of tests to run on stable

These tests all relied on support which has now ridden to stable at this
point, so let's let them run on stable!

Author: alexcrichton

tests/testsuite/build.rs

@@ -4540,10 +4540,6 @@ Caused by:
 
 #[cargo_test]
 fn tricky_pipelining() {
-    if !cargo_test_support::is_nightly() {
-        return;
-    }
-
     let foo = project()
         .file(
             "Cargo.toml",
@@ -4570,10 +4566,6 @@ fn tricky_pipelining() {
 
 #[cargo_test]
 fn pipelining_works() {
-    if !cargo_test_support::is_nightly() {
-        return;
-    }
-
     let foo = project()
         .file(
             "Cargo.toml",
@@ -4605,10 +4597,6 @@ fn pipelining_works() {
 
 #[cargo_test]
 fn pipelining_big_graph() {
-    if !cargo_test_support::is_nightly() {
-        return;
-    }
-
     // Create a crate graph of the form {a,b}{0..29}, where {a,b}(n) depend on {a,b}(n+1)
     // Then have `foo`, a binary crate, depend on the whole thing.
     let mut project = project()

tests/testsuite/fix.rs

@@ -1,7 +1,7 @@
 use std::fs::File;
 
 use cargo_test_support::git;
-use cargo_test_support::{basic_manifest, clippy_is_available, is_nightly, project};
+use cargo_test_support::{basic_manifest, clippy_is_available, project};
 
 use std::io::Write;
 
@@ -1251,12 +1251,6 @@ fn fix_in_existing_repo_weird_ignore() {
 
 #[cargo_test]
 fn fix_with_clippy() {
-    if !is_nightly() {
-        // fix --clippy is unstable
-        eprintln!("skipping test: requires nightly");
-        return;
-    }
-
     if !clippy_is_available() {
         return;
     }

tests/testsuite/message_format.rs

@@ -2,10 +2,6 @@ use cargo_test_support::{basic_manifest, project};
 
 #[cargo_test]
 fn cannot_specify_two() {
-    if !cargo_test_support::is_nightly() {
-        return;
-    }
-
     let p = project()
         .file("Cargo.toml", &basic_manifest("foo", "0.1.0"))
         .file("src/main.rs", "fn main() {}")
@@ -26,10 +22,6 @@ fn cannot_specify_two() {
 
 #[cargo_test]
 fn double_json_works() {
-    if !cargo_test_support::is_nightly() {
-        return;
-    }
-
     let p = project()
         .file("Cargo.toml", &basic_manifest("foo", "0.1.0"))
         .file("src/main.rs", "fn main() {}")
@@ -51,10 +43,6 @@ fn double_json_works() {
 
 #[cargo_test]
 fn cargo_renders() {
-    if !cargo_test_support::is_nightly() {
-        return;
-    }
-
     let p = project()
         .file(
             "Cargo.toml",
@@ -87,10 +75,6 @@ error[..]`main`[..]
 
 #[cargo_test]
 fn cargo_renders_short() {
-    if !cargo_test_support::is_nightly() {
-        return;
-    }
-
     let p = project()
         .file("Cargo.toml", &basic_manifest("foo", "0.1.0"))
         .file("src/main.rs", "")
@@ -110,10 +94,6 @@ error[..]`main`[..]
 
 #[cargo_test]
 fn cargo_renders_ansi() {
-    if !cargo_test_support::is_nightly() {
-        return;
-    }
-
     let p = project()
         .file("Cargo.toml", &basic_manifest("foo", "0.1.0"))
         .file("src/main.rs", "")

tests/testsuite/profile_config.rs

@@ -1,4 +1,4 @@
-use cargo_test_support::{basic_lib_manifest, is_nightly, paths, project};
+use cargo_test_support::{basic_lib_manifest, paths, project};
 
 #[cargo_test]
 fn profile_config_gated() {
@@ -230,11 +230,6 @@ found profile override specs: bar, bar:0.5.0",
 
 #[cargo_test]
 fn profile_config_all_options() {
-    if !is_nightly() {
-        // May be removed once 1.34 is stable (added support for incremental-LTO).
-        return;
-    }
-
     // Ensure all profile options are supported.
     let p = project()
         .file("src/main.rs", "fn main() {}")

tests/testsuite/timings.rs

@@ -1,13 +1,8 @@
+use cargo_test_support::project;
 use cargo_test_support::registry::Package;
-use cargo_test_support::{is_nightly, project};
 
 #[cargo_test]
 fn timings_works() {
-    if !is_nightly() {
-        // Requires --json flag, remove this check in 1.38.
-        return;
-    }
-
     Package::new("dep", "0.1.0").publish();
 
     let p = project()