some clippy::performance fixes

use vec![] instead of Vec::new() +  push()
avoid redundant clones
use chars instead of &str for single char patterns in ends_with() and starts_with()
allocate some Vecs with capacity to avoid unneccessary resizing

crates/proc_macro_api/src/version.rs

@@ -33,7 +33,7 @@ pub(crate) fn read_info(dylib_path: &Path) -> io::Result<RustCInfo> {
     }
 
     let version_part = items.next().ok_or(err!("no version string"))?;
-    let mut version_parts = version_part.split("-");
+    let mut version_parts = version_part.split('-');
     let version = version_parts.next().ok_or(err!("no version"))?;
     let channel = version_parts.next().unwrap_or_default().to_string();
 
@@ -51,7 +51,7 @@ pub(crate) fn read_info(dylib_path: &Path) -> io::Result<RustCInfo> {
     let date = date[0..date.len() - 2].to_string();
 
     let version_numbers = version
-        .split(".")
+        .split('.')
         .map(|it| it.parse::<usize>())
         .collect::<Result<Vec<_>, _>>()
         .map_err(|_| err!("version number error"))?;