samCliLocalInvoke.ts: fix environment spec

Problem: ENOENT error during the "sam invoke" step when attempting to
debug, which causes SAM debug to fail:

    Building SAM Application...
    Build complete.
    Starting the SAM Application locally (see Terminal for output)
    Running command: sam local invoke awsToolkitSamLocalResource --template … --event … --env-vars … -d 5883
    Error running local SAM Application: spawn sam ENOENT
    Waiting for SAM Application to start before attaching debugger...
    Local invoke of SAM Application has ended.

Solution: When setting env vars one must also copy the current
environment, else it is discarded.

NB: the localLambdaRunner.ts change is not directly related.

Author: justinmk3

src/shared/sam/cli/samCliLocalInvoke.ts

@@ -217,7 +217,10 @@ export class SamCliLocalInvokeInvocation {
 
         await this.args.invoker.invoke({
             options: {
-                env: this.args.environmentVariables,
+                env: {
+                    ...process.env,
+                    ...this.args.environmentVariables,
+                },
             },
             command: 'sam',
             args: invokeArgs,

src/shared/sam/localLambdaRunner.ts

@@ -154,6 +154,7 @@ export async function invokeLambdaFunction(
     if (!config.noDebug) {
         // Needed at least for dotnet case; harmless for others.
         samCliArgs.environmentVariables = {
+            ...samCliArgs.environmentVariables,
             SAM_BUILD_MODE: 'debug',
         }
     }

src/shared/utilities/childProcess.ts

@@ -73,6 +73,12 @@ export class ChildProcess {
         }
 
         getLogger().info(`Running command: ${this.process} ${this.args.join(' ')}`)
+
+        // Async.
+        // See also crossSpawn.spawnSync().
+        // Arguments are forwarded[1] to node `child_process` module, see its documentation[2].
+        // [1] https://github.com/moxystudio/node-cross-spawn/blob/master/index.js
+        // [2] https://nodejs.org/api/child_process.html
         this.childProcess = crossSpawn(this.process, this.args, this.options)
 
         this.childProcess.stdout?.on('data', (data: { toString(): string }) => {