Disable snapshot types on Android. (#994)

Snapshot types are used by Xcode 16. They are not needed on non-Apple
platforms. This PR disables them on Android by setting
`SWT_NO_SNAPSHOT_TYPES`.

### Checklist:

- [x] Code and documentation should follow the style of the [Style
Guide](https://github.com/apple/swift-testing/blob/main/Documentation/StyleGuide.md).
- [x] If public symbols are renamed or modified, DocC references should
be updated.

Author: grynspan

Package.swift

@@ -191,7 +191,7 @@ extension Array where Element == PackageDescription.SwiftSetting {
 
       .define("SWT_NO_EXIT_TESTS", .when(platforms: [.iOS, .watchOS, .tvOS, .visionOS, .wasi, .android])),
       .define("SWT_NO_PROCESS_SPAWNING", .when(platforms: [.iOS, .watchOS, .tvOS, .visionOS, .wasi, .android])),
-      .define("SWT_NO_SNAPSHOT_TYPES", .when(platforms: [.linux, .custom("freebsd"), .openbsd, .windows, .wasi])),
+      .define("SWT_NO_SNAPSHOT_TYPES", .when(platforms: [.linux, .custom("freebsd"), .openbsd, .windows, .wasi, .android])),
       .define("SWT_NO_DYNAMIC_LINKING", .when(platforms: [.wasi])),
       .define("SWT_NO_PIPES", .when(platforms: [.wasi])),
     ]
@@ -248,7 +248,7 @@ extension Array where Element == PackageDescription.CXXSetting {
     result += [
       .define("SWT_NO_EXIT_TESTS", .when(platforms: [.iOS, .watchOS, .tvOS, .visionOS, .wasi, .android])),
       .define("SWT_NO_PROCESS_SPAWNING", .when(platforms: [.iOS, .watchOS, .tvOS, .visionOS, .wasi, .android])),
-      .define("SWT_NO_SNAPSHOT_TYPES", .when(platforms: [.linux, .custom("freebsd"), .openbsd, .windows, .wasi])),
+      .define("SWT_NO_SNAPSHOT_TYPES", .when(platforms: [.linux, .custom("freebsd"), .openbsd, .windows, .wasi, .android])),
       .define("SWT_NO_DYNAMIC_LINKING", .when(platforms: [.wasi])),
       .define("SWT_NO_PIPES", .when(platforms: [.wasi])),
     ]