bootstrap: tweak verbosity settings

Currently the verbosity settings are:
- 2: RUSTC-SHIM envvars get spammed on every invocation, O(30) lines
     cargo is passed -v which outputs CLI invocations, O(5) lines
- 3: cargo is passed -vv which outputs build script output, O(0-10) lines

This commit changes it to:

- 1: cargo is passed -v, O(5) lines
- 2: cargo is passed -vv, O(10) lines
- 3: RUSTC-SHIM envvars get spammed, O(30) lines

src/bootstrap/bin/rustc.rs

@@ -146,7 +146,7 @@ fn main() {
     }
 
     let is_test = args.iter().any(|a| a == "--test");
-    if verbose > 1 {
+    if verbose > 2 {
         let rust_env_vars =
             env::vars().filter(|(k, _)| k.starts_with("RUST") || k.starts_with("CARGO"));
         let prefix = if is_test { "[RUSTC-SHIM] rustc --test" } else { "[RUSTC-SHIM] rustc" };

src/bootstrap/bootstrap.py

@@ -959,7 +959,7 @@ class RustBuild(object):
                 self.cargo()))
         args = [self.cargo(), "build", "--manifest-path",
                 os.path.join(self.rust_root, "src/bootstrap/Cargo.toml")]
-        for _ in range(1, self.verbose):
+        for _ in range(0, self.verbose):
             args.append("--verbose")
         if self.use_locked_deps:
             args.append("--locked")

src/bootstrap/builder.rs

@@ -1483,7 +1483,7 @@ impl<'a> Builder<'a> {
             cargo.env("WINAPI_NO_BUNDLED_LIBRARIES", "1");
         }
 
-        for _ in 1..self.verbosity {
+        for _ in 0..self.verbosity {
             cargo.arg("-v");
         }