Adds a `pragma('vm:entry-point')` to the synthesized library and makes
the tree-shakers respect that pragma on `library`s.
TEST=tests/ffi/native_assets/asset_relative_test.dart
Bug: Found in g3.
Change-Id: I1bc63b42ab867a5f1d2e7f9da4842de59f3d5c1d
Cq-Include-Trybots: dart/try:vm-aot-asan-linux-release-x64-try,vm-aot-linux-debug-x64-try,vm-aot-linux-debug-x64c-try,vm-aot-mac-release-arm64-try,vm-aot-mac-release-x64-try,vm-aot-msan-linux-release-x64-try,vm-aot-obfuscate-linux-release-x64-try,vm-aot-optimization-level-linux-release-x64-try,vm-aot-tsan-linux-release-x64-try,vm-aot-ubsan-linux-release-x64-try,vm-aot-win-debug-arm64-try,vm-aot-win-debug-x64-try,vm-aot-win-debug-x64c-try,vm-asan-linux-release-arm64-try,vm-msan-linux-release-arm64-try,vm-tsan-linux-release-arm64-try,vm-ubsan-linux-release-arm64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/377442
Auto-Submit: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Commit-Queue: Daco Harkes <dacoharkes@google.com>
Daco Harkes
4730365bde