Strip debug symbols from ELF library snapshots (flutter#34250)

AOT compiled code is now packaged as an ELF library for Android targets.
By default gen_snapshot's output contains debug symbols.  The symbols could
be stripped as a separate step, but that requires NDK tools that the user
may not have available.

This change passes a gen_snapshot flag that omits the symbols, and it filters
out a warning printed when that flag is used.

Author: jason-simmons

packages/flutter_tools/lib/src/base/build.dart

@@ -63,7 +63,17 @@ class GenSnapshot {
       final String hostArch = iosArch == IOSArch.armv7 ? '-i386' : '-x86_64';
       return runCommandAndStreamOutput(<String>['/usr/bin/arch', hostArch, snapshotterPath]..addAll(args));
     }
-    return runCommandAndStreamOutput(<String>[snapshotterPath]..addAll(args));
+
+    StringConverter outputFilter;
+    if (additionalArgs.contains('--strip')) {
+      // Filter out gen_snapshot's warning message about stripping debug symbols
+      // from ELF library snapshots.
+      const String kStripWarning = 'Warning: Generating ELF library without DWARF debugging information.';
+      outputFilter = (String line) => line != kStripWarning ? line : null;
+    }
+
+    return runCommandAndStreamOutput(<String>[snapshotterPath]..addAll(args),
+                                     mapFunction: outputFilter);
   }
 }
 
@@ -138,6 +148,7 @@ class AOTSnapshotter {
       outputPaths.add(aotSharedLibrary);
       genSnapshotArgs.add('--snapshot_kind=app-aot-elf');
       genSnapshotArgs.add('--elf=$aotSharedLibrary');
+      genSnapshotArgs.add('--strip');
     } else {
       // Blob AOT snapshot.
       final String vmSnapshotData = fs.path.join(outputDir.path, 'vm_snapshot_data');

packages/flutter_tools/test/base/build_test.dart

@@ -418,6 +418,7 @@ void main() {
         '--deterministic',
         '--snapshot_kind=app-aot-elf',
         '--elf=build/foo/app.so',
+        '--strip',
         '--no-sim-use-hardfp',
         '--no-use-integer-division',
         'main.dill',
@@ -447,6 +448,7 @@ void main() {
         '--deterministic',
         '--snapshot_kind=app-aot-elf',
         '--elf=build/foo/app.so',
+        '--strip',
         'main.dill',
       ]);
     }, overrides: contextOverrides);