Allow C symbol file to be arch variant

The libclang_rt.* prebuilt libraries have an autogenerated map.txt for
each arch. e.g.
```
$ ls prebuilts/clang/host/linux-x86/clang-r530567/lib/clang/19/lib/linux/libclang_rt.asan*map.txt
prebuilts/clang/host/linux-x86/clang-r530567/lib/clang/19/lib/linux/libclang_rt.asan-aarch64-android.map.txt  prebuilts/clang/host/linux-x86/clang-r530567/lib/clang/19/lib/linux/libclang_rt.asan-riscv64-android.map.txt
prebuilts/clang/host/linux-x86/clang-r530567/lib/clang/19/lib/linux/libclang_rt.asan-arm-android.map.txt      prebuilts/clang/host/linux-x86/clang-r530567/lib/clang/19/lib/linux/libclang_rt.asan-x86_64-android.map.txt
prebuilts/clang/host/linux-x86/clang-r530567/lib/clang/19/lib/linux/libclang_rt.asan-i686-android.map.txt
```

These map.txt files are currently a noop, but will be used to compile
stub srcs. In preparation for that, make stubs.symbol_file and
llndk.symbol_file arch variant

Test: m nothing # no diff in ninja file
Bug: 220898484
Change-Id: I7316546905c1327c764ee67a48c77a2a68465d77