The newly generated libstdcxx.modulemap clashes with the libc++ modulemap on Android

[finagolfin]

Describe the bug
#41953 added a new C++ module map, but it is not needed for Android and causes errors like these on the Android CI:

/home/ubuntu/jenkins/workspace/oss-swift-RA-linux-ubuntu-16.04-android-arm64/buildbot_linux/swift-linux-x86_64/lib/swift/android/aarch64/libstdcxx.modulemap:19:8: error: redefinition of module 'std'                                                
module std {                        
/home/ubuntu/android-ndk-r19c/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include/c++/v1/module.modulemap:8:8: note: previously defined here

To Reproduce

1. Run one of the failing CI tests or the equivalent.

Expected behavior
Be able to import C++ without this error.

Environment:

• OS: Android

Additional context
I've submitted a fix in #58497.

[finagolfin]

The community Android CI no longer shows this error, after my fix in #58497, so this works now.