Update Travis Tests to run platforms in parallel (#11256)

buildroot/bin/env_clean

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+
+if [ -d ".pioenvs" ]; then
+  rm -r .pioenvs
+fi
+
+if [ -d ".piolibdeps" ]; then
+  rm -r .piolibdeps
+fi
+
+if [ -d ".piolib" ]; then
+  rm -r .piolib
+fi
+
+if [ ! -z "$1" ]; then
+  if [ $1 = "--deep" ]; then
+    if [ -d "~/.platformio/packages" ]; then
+      rm -r ~/.platformio/packages/*
+    fi
+
+    if [ -d "~/.platformio/platforms" ]; then
+      rm -r ~/.platformio/platforms/*
+    fi
+
+    if [ -d "~/.platformio/.cache" ]; then
+      rm -r ~/.platformio/.cache/*
+    fi
+  fi
+fi