allowing overriding USE_ANDROIDX_REMOTE_BUILD_CACHE for studio integration branch

in case anyone wants to run a build with cache disabled.

This might be helpful in case the cache isn't working yet due to potentially waiting for permissions to update

Test: Treehugger runs busytown/androidx-studio-integration-lint.sh

Change-Id: I7a593cd400ab8fdf0fbe88be2830692d5ba76b20
diff --git a/busytown/impl/build-studio-and-androidx.sh b/busytown/impl/build-studio-and-androidx.sh
index 0003d61..2d87b18 100755
--- a/busytown/impl/build-studio-and-androidx.sh
+++ b/busytown/impl/build-studio-and-androidx.sh
@@ -95,7 +95,9 @@
 export JAVA_HOME="$(pwd)/prebuilts/jdk/jdk11/$PREBUILT_JDK/"
 export JAVA_TOOLS_JAR="$(pwd)/prebuilts/jdk/jdk8/$PREBUILT_JDK/lib/tools.jar"
 export LINT_PRINT_STACKTRACE=true
-export USE_ANDROIDX_REMOTE_BUILD_CACHE=gcp
+if [ "$USE_ANDROIDX_REMOTE_BUILD_CACHE" == "" ]; then
+  export USE_ANDROIDX_REMOTE_BUILD_CACHE=gcp
+fi
 
 function buildAndroidx() {
   RETURN_CODE=0