vscode convenience improvements

.gitignore

@@ -16,6 +16,12 @@ rusty-tags.*
 .cproject
 .project
 
+# Clangd creates this to cache its results
+.cache/
+
+# The code cache is a transient file.
+compile_commands.json
+
 # Compiled python modules.
 *.pyc
 

Cargo.toml

@@ -2,6 +2,7 @@
 members = ["sim"]
 exclude = ["ptest"]
 resolver = "2"
+default-members = ["sim"]
 
 # The simulator runs very slowly without optimization.  A value of 1
 # compiles in about half the time, but runs about 5-6 times slower.  2

docs/release-notes.d/vscode.md

@@ -0,0 +1,2 @@
+- A few changes to make vscode nicer, including a default package to build at
+  the top level, and ignoring some of the cache files from vscode.