Move response file handling to a separate package

sbox is going to need to read and write response files, move ReadRspFile
to its own package.

Test: response_test.go
Change-Id: Iecb5486b4aaeb2531828743ad8ef784df675e18e
diff --git a/response/Android.bp b/response/Android.bp
new file mode 100644
index 0000000..e19981f
--- /dev/null
+++ b/response/Android.bp
@@ -0,0 +1,16 @@
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+bootstrap_go_package {
+    name: "soong-response",
+    pkgPath: "android/soong/response",
+    deps: [
+    ],
+    srcs: [
+        "response.go",
+    ],
+    testSrcs: [
+        "response_test.go",
+    ],
+}