Generate apex_available from c2a instead of a patch am: 01ff0c6d2e am: 0a44958a3e am: ab3823c0e4

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/memoffset/+/1688983

Change-Id: Ic9fc94c8593a98f90982853628638cb634ed4a6b
diff --git a/Android.bp b/Android.bp
index ae913ce..d53b9c9 100644
--- a/Android.bp
+++ b/Android.bp
@@ -1,4 +1,4 @@
-// This file is generated by cargo2android.py --run --device --tests --dependencies --patch=patches/Android.bp.patch.
+// This file is generated by cargo2android.py --config cargo2android.json.
 // Do not modify this file as changes will be overridden on upgrade.
 
 package {
@@ -25,11 +25,12 @@
     srcs: ["src/lib.rs"],
     edition: "2015",
     features: ["default"],
-    flags: [
-        "--cfg allow_clippy",
-        "--cfg doctests",
-        "--cfg maybe_uninit",
-        "--cfg tuple_ty",
+    cfgs: [
+        "allow_clippy",
+        "doctests",
+        "maybe_uninit",
+        "raw_ref_macros",
+        "tuple_ty",
     ],
     apex_available: [
         "//apex_available:platform",
@@ -45,11 +46,12 @@
     auto_gen_config: true,
     edition: "2015",
     features: ["default"],
-    flags: [
-        "--cfg allow_clippy",
-        "--cfg doctests",
-        "--cfg maybe_uninit",
-        "--cfg tuple_ty",
+    cfgs: [
+        "allow_clippy",
+        "doctests",
+        "maybe_uninit",
+        "raw_ref_macros",
+        "tuple_ty",
     ],
     rustlibs: [
         // ANDROID: disable for now just to avoid another dependency.
diff --git a/cargo2android.json b/cargo2android.json
new file mode 100644
index 0000000..0f253f0
--- /dev/null
+++ b/cargo2android.json
@@ -0,0 +1,11 @@
+{
+  "apex-available": [
+    "//apex_available:platform",
+    "com.android.virt"
+  ],
+  "dependencies": true,
+  "device": true,
+  "patch": "patches/Android.bp.patch",
+  "run": true,
+  "tests": true
+}
\ No newline at end of file
diff --git a/patches/Android.bp.patch b/patches/Android.bp.patch
index 76d4a07..96c3e12 100644
--- a/patches/Android.bp.patch
+++ b/patches/Android.bp.patch
@@ -2,18 +2,7 @@
 index eb63f7c..efa8362 100644
 --- a/Android.bp
 +++ b/Android.bp
-@@ -13,6 +13,10 @@ rust_library {
-         "--cfg maybe_uninit",
-         "--cfg tuple_ty",
-     ],
-+    apex_available: [
-+        "//apex_available:platform",
-+        "com.android.virt",
-+    ],
- }
- 
- rust_defaults {
-@@ -30,7 +34,8 @@ rust_defaults {
+@@ -48,7 +52,8 @@ rust_defaults {
          "--cfg tuple_ty",
      ],
      rustlibs: [