disable r64 for glibc testing llvm job

```
   : && /usr/bin/clang-19 --target=riscv64-pc-linux-gnu -Wno-unused-command-line-argument  -fstrict-flex-arrays=3 -fstack-protector-all -fPIC -fno-omit-frame-pointer -fvisibility=hidden -fno-semantic-interposition -fno-unwind-tables -fno-asynchronous-unwind-tables -ffunction-sections -fdata-sections -isystem /usr/riscv64-linux-gnu/include  -D_FORTIFY_SOURCE=2  -Wl,-z,relro,-z,now -Wl,-z,noexecstack -Wl,-z,nodlopen -Wl,-Bsymbolic -Wl,--gc-sections -Wl,--icf=all -L/usr/riscv64-linux-gnu/lib -L/usr/lib/gcc-cross/riscv64-linux-gnu/14 -fuse-ld=lld-19 -Wl,-s -Wl,--build-id=none  CMakeFiles/cmTC_5fec7.dir/testCCompiler.c.o -o cmTC_5fec7   && :
    ld.lld-19: error: cannot open Scrt1.o: No such file or directory
    ld.lld-19: error: cannot open crti.o: No such file or directory
    ld.lld-19: error: cannot open crtbeginS.o: No such file or directory
    ld.lld-19: error: cannot open crtendS.o: No such file or directory
    ld.lld-19: error: cannot open crtn.o: No such file or directory
    clang-19: error: linker command failed with exit code 1 (use -v to see invocation)
    ninja: build stopped: subcommand failed.
```
https://github.com/curl/curl-for-win/actions/runs/11383761271/job/31670070246#step:3:3632

.github/workflows/build.yml

@@ -66,7 +66,7 @@ jobs:
           fetch-depth: '300'
       - name: 'build'
         run: |
-          export CW_CONFIG='${{ github.ref_name }}-linux-a64-r64-x64'
+          export CW_CONFIG='${{ github.ref_name }}-linux-a64-x64'
           export CW_REVISION='${{ github.sha }}'
           . ./_versions.sh
           docker trust inspect --pretty "${DOCKER_IMAGE}"