Add RA_WAIT_DBG and docs

crates/rust-analyzer/src/bin/args.rs

@@ -57,6 +57,7 @@ FLAGS:
 ENVIRONMENTAL VARIABLES:
     RA_LOG            Set log filter in env_logger format
     RA_PROFILE        Enable hierarchical profiler
+    RA_WAIT_DBG       If set acts like a --wait-dbg flag
 
 COMMANDS:
 

crates/rust-analyzer/src/bin/main.rs

@@ -29,7 +29,7 @@ fn main() {
 
 fn try_main() -> Result<()> {
     let args = args::Args::parse()?;
-    if args.wait_dbg {
+    if args.wait_dbg || env::var("RA_WAIT_DBG").is_ok() {
         #[allow(unused_mut)]
         let mut d = 4;
         while d == 4 {