Add lldb smoke test (#1241)

* add lldb runner

* don't build wasmtime

* use brew's lldb

* disable for macos

* set LLDB on linux

* re-org gh actions and cfg

* address feedback

.github/actions/define-dwarfdump-env/README.md

@@ -1,3 +0,0 @@
-# define-dwarfdump-env
-
-Defines `DWARFDUMP` path executable.

.github/actions/define-llvm-env/README.md

@@ -0,0 +1,3 @@
+# define-llvm-env
+
+Defines `DWARFDUMP` and `LLDB` path executable.

.github/actions/define-llvm-env/main.js

@@ -3,9 +3,11 @@
 // On OSX pointing to brew's LLVM location.
 if (process.platform == 'darwin') {
   console.log("::set-env name=DWARFDUMP::/usr/local/opt/llvm/bin/llvm-dwarfdump");
+  console.log("::set-env name=LLDB::/usr/local/opt/llvm/bin/lldb");
 }
 
 // On Linux pointing to specific version
 if (process.platform == 'linux') {
   console.log("::set-env name=DWARFDUMP::/usr/bin/llvm-dwarfdump-9");
+  console.log("::set-env name=LLDB::/usr/bin/lldb-9");
 }