Change env var used for testing Clippy

This changes the variable used for testing Clippy in the internal test
suite:

```
CLIPPY_TESTS -> __CLIPPY_INTERNAL_TESTS
```

`CLIPPY_TESTS` is understandably used in environments of Clippy users,
so we shouldn't use it in our test suite.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/driver.rs b/src/driver.rs
index e490ee54c0b..f5f6c09ed8e 100644
--- a/src/driver.rs
+++ b/src/driver.rs
@@ -298,7 +298,7 @@ pub fn main() {
         // - IF Clippy is run on the main crate, not on deps (`!cap_lints_allow`) THEN
         //    - IF `--no-deps` is not set (`!no_deps`) OR
         //    - IF `--no-deps` is set and Clippy is run on the specified primary package
-        let clippy_tests_set = env::var("CLIPPY_TESTS").map_or(false, |val| val == "true");
+        let clippy_tests_set = env::var("__CLIPPY_INTERNAL_TESTS").map_or(false, |val| val == "true");
         let cap_lints_allow = arg_value(&orig_args, "--cap-lints", |val| val == "allow").is_some();
         let in_primary_package = env::var("CARGO_PRIMARY_PACKAGE").is_ok();