Allow specifying what proc-macro server to run in rust_analyzer::load_cargo API

crates/rust-analyzer/src/cli/analysis_stats.rs

@@ -33,7 +33,7 @@ use vfs::{AbsPathBuf, Vfs, VfsPath};
 
 use crate::cli::{
     flags::{self, OutputFormat},
-    load_cargo::{load_workspace, LoadCargoConfig},
+    load_cargo::{load_workspace, LoadCargoConfig, ProcMacroServerChoice},
     print_memory_usage,
     progress_report::ProgressReport,
     report_metric, Result, Verbosity,
@@ -59,11 +59,6 @@ impl flags::AnalysisStats {
             true => None,
             false => Some(RustcSource::Discover),
         };
-        let load_cargo_config = LoadCargoConfig {
-            load_out_dirs_from_check: !self.disable_build_scripts,
-            with_proc_macro: !self.disable_proc_macros,
-            prefill_caches: false,
-        };
         let no_progress = &|_| ();
 
         let mut db_load_sw = self.stop_watch();
@@ -73,6 +68,11 @@ impl flags::AnalysisStats {
 
         let mut workspace = ProjectWorkspace::load(manifest, &cargo_config, no_progress)?;
         let metadata_time = db_load_sw.elapsed();
+        let load_cargo_config = LoadCargoConfig {
+            load_out_dirs_from_check: !self.disable_build_scripts,
+            with_proc_macro_server: ProcMacroServerChoice::Sysroot,
+            prefill_caches: false,
+        };
 
         let build_scripts_time = if self.disable_build_scripts {
             None