Add support for Android 11 RefBase ABI (#29)

Implements a compatibility layer to allow the binary to run on
Android 11 (API 30) and older, which lack the `incStrongRequireStrong`
symbol in their `libutils.so`.

This is achieved by creating a runtime wrapper that checks the device's
SDK version.
- On Android 12 (API 31) and newer, it dynamically loads and calls the
  `incStrongRequireStrong` function using `dlsym`.
- On older versions, it safely falls back to the universally available
  `incStrong` method.

This resolves the fatal `dlopen` error "cannot locate symbol" when
injecting the library into processes on older Android versions.

See AOSP change
https://android-review.googlesource.com/c/platform/system/core/+/1660499

app/src/main/cpp/CMakeLists.txt

@@ -12,7 +12,7 @@ add_subdirectory(external/LSPlt/lsplt/src/main/jni)
 
 add_compile_definitions(BINDER_DISABLE_NATIVE_HANDLE)
 add_library(utils SHARED stub/stub_utils.cpp)
-target_include_directories(utils PUBLIC external/AOSP/include)
+target_include_directories(utils PUBLIC external/AOSP/include compat)
 
 add_library(binder SHARED stub/stub_binder.cpp)
 target_include_directories(binder PUBLIC external/AOSP/include)
@@ -22,7 +22,7 @@ add_executable(libinject.so inject/main.cpp inject/utils.cpp)
 target_include_directories(libinject.so PUBLIC include)
 target_link_libraries(libinject.so PRIVATE lsplt_static)
 
-add_library(${CMAKE_PROJECT_NAME} SHARED binder_interceptor.cpp)
+add_library(${CMAKE_PROJECT_NAME} SHARED binder_interceptor.cpp compat/refbase_compat.cpp)
 target_include_directories(${CMAKE_PROJECT_NAME} PUBLIC external/linux-kernel/include include)
 target_link_libraries(${CMAKE_PROJECT_NAME} PRIVATE binder lsplt_static utils)