Determine GC type based on BUILT_KERNEL_VERSION_FILE.

How it works:
1. build/make/core/Makefile generates a txt file with the kernel
   version, which is taken from an explicit BOARD_KERNEL_VERSION value,
   or extracted from the kernel image on the source tree, or extracted
   from the kernel image extracted from the prebuilt boot.img.
   The file is saved at
   $ANDROID_PRODUCT_OUT/obj/PACKAGING/check_vintf_all_intermediates/kernel_version.txt.
2. If PRODUCT_ENABLE_UFFD_GC is "default", meaning the GC type needs to
   be determined by the kernel version, build/make/core/Makefile copies
   kernel_version.txt to
   out/soong/dexpreopt/kernel_version_for_uffd_gc.txt.
3. build/soong/dexpreopt/config.go writes the the UFFD GC flag to
   out/soong/dexpreopt/uffd_gc_flag.txt. The flag is determined by an
   explicit PRODUCT_ENABLE_UFFD_GC value or by contruct_uffd_gc_flag.py,
   which reads kernel_version_for_uffd_gc.txt and determines the flag
   accordingly.
4. dex2oat takes the UFFD GC flag from uffd_gc_flag.txt.
5. post_process_props.py mangles ro.dalvik.vm.enable_uffd_gc based on
   the same logic.

Bug: 321751629
Bug: 319554951
Bug: 318763448
Bug: 319648491
Test: m --no-skip-soong-tests nothing
Test: atest uffd_gc_utils_test
Test: Build with `OVERRIDE_ENABLE_UFFD_GC=default m` for device with no
  UFFD support -
  1. Check the existence of `-Xgc:CMC` in
     out/soong/dexpreopt_arm64/dex_bootjars/android/system/framework/arm64/boot.invocation
     (dex2oat invocation for a boot image)
  2. Check the existence of `-Xgc:CMC` in
     out/soong/.intermediates/packages/apps/Settings/Settings/android_common/dexpreopt/Settings/oat/arm64/package.invocation
     (dex2oat invocation for an app defined in .bp)
  3. Check the existence of `-Xgc:CMC` in
     $ANDROID_PRODUCT_OUT/obj/APPS/Dialer_intermediates/oat/arm64/package.invocation
     (dex2oat invocation for an app defined in .mk)
  4. Check the value of ro.dalvik.vm.enable_uffd_gc in
     $ANDROID_PRODUCT_OUT/product/etc/build.prop
Test: Build with `OVERRIDE_ENABLE_UFFD_GC=default m` for device with
  UFFD support, and do the steps above.
Test: Build with `OVERRIDE_ENABLE_UFFD_GC=true m`, and do the steps
  above.
Test: Build with `OVERRIDE_ENABLE_UFFD_GC=false m`, and do the steps
  above.

Change-Id: I8df6e5be1644da05d2d5c57b3520f29601dfd7a4

tools/Android.bp

@@ -18,56 +18,65 @@ package {
 }
 
 python_binary_host {
-  name: "generate-self-extracting-archive",
-  srcs: ["generate-self-extracting-archive.py"],
+    name: "generate-self-extracting-archive",
+    srcs: ["generate-self-extracting-archive.py"],
 }
 
 python_binary_host {
-  name: "post_process_props",
-  srcs: ["post_process_props.py"],
+    name: "post_process_props",
+    srcs: ["post_process_props.py"],
+    libs: [
+        "uffd_gc_utils",
+    ],
 }
 
 python_test_host {
-  name: "post_process_props_unittest",
-  main: "test_post_process_props.py",
-  srcs: [
-    "post_process_props.py",
-    "test_post_process_props.py",
-  ],
-  test_config: "post_process_props_unittest.xml",
-  test_suites: ["general-tests"],
+    name: "post_process_props_unittest",
+    main: "test_post_process_props.py",
+    srcs: [
+        "post_process_props.py",
+        "test_post_process_props.py",
+    ],
+    libs: [
+        "uffd_gc_utils",
+    ],
+    test_config: "post_process_props_unittest.xml",
+    test_suites: ["general-tests"],
 }
 
 python_binary_host {
-  name: "extract_kernel",
-  srcs: ["extract_kernel.py"],
+    name: "extract_kernel",
+    srcs: ["extract_kernel.py"],
 }
 
 genrule_defaults {
-  name: "extract_kernel_release_defaults",
-  tools: ["extract_kernel", "lz4"],
-  out: ["kernel_release.txt"],
-  cmd: "$(location) --tools lz4:$(location lz4) --input $(in) --output-release > $(out)"
+    name: "extract_kernel_release_defaults",
+    tools: [
+        "extract_kernel",
+        "lz4",
+    ],
+    out: ["kernel_release.txt"],
+    cmd: "$(location) --tools lz4:$(location lz4) --input $(in) --output-release > $(out)",
 }
 
 cc_binary_host {
-  name: "build-runfiles",
-  srcs: ["build-runfiles.cc"],
+    name: "build-runfiles",
+    srcs: ["build-runfiles.cc"],
 }
 
 python_binary_host {
-  name: "check_radio_versions",
-  srcs: ["check_radio_versions.py"],
+    name: "check_radio_versions",
+    srcs: ["check_radio_versions.py"],
 }
 
 python_binary_host {
-  name: "check_elf_file",
-  srcs: ["check_elf_file.py"],
+    name: "check_elf_file",
+    srcs: ["check_elf_file.py"],
 }
 
 python_binary_host {
-  name: "generate_gts_shared_report",
-  srcs: ["generate_gts_shared_report.py"],
+    name: "generate_gts_shared_report",
+    srcs: ["generate_gts_shared_report.py"],
 }
 
 python_binary_host {
@@ -77,10 +86,10 @@ python_binary_host {
         "list_files.py",
     ],
     version: {
-      py3: {
-        embedded_launcher: true,
-      }
-    }
+        py3: {
+            embedded_launcher: true,
+        },
+    },
 }
 
 python_test_host {
@@ -98,11 +107,11 @@ python_test_host {
 }
 
 python_binary_host {
-  name: "characteristics_rro_generator",
-  srcs: ["characteristics_rro_generator.py"],
-  version: {
-    py3: {
-      embedded_launcher: true,
+    name: "characteristics_rro_generator",
+    srcs: ["characteristics_rro_generator.py"],
+    version: {
+        py3: {
+            embedded_launcher: true,
+        },
     },
-  },
 }