[clang] [Fuchsia] Enable OpenCSD by default for Fuchsia (PR #195194)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-ppc64le-linux-test-suite` running on `ppc64le-clang-test-suite` while building `clang` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/95/builds/20760

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
...
PASS: Clang :: Preprocessor/riscv-target-features.c (110222 of 110232)
PASS: LLVM :: tools/llvm-objdump/ELF/AMDGPU/subtarget.ll (110223 of 110232)
PASS: Clang :: Driver/range-warnings.c (110224 of 110232)
PASS: Clang :: Driver/linux-ld.c (110225 of 110232)
PASS: LLVM :: CodeGen/RISCV/attributes.ll (110226 of 110232)
PASS: LLVM :: tools/llvm-readobj/ELF/note-core.test (110227 of 110232)
PASS: Clang :: Driver/arm-cortex-cpus-1.c (110228 of 110232)
PASS: ScudoStandalone-Unit :: ./ScudoUnitTest-powerpc64le-Test/102/366 (110229 of 110232)
PASS: Clang :: Driver/arm-cortex-cpus-2.c (110230 of 110232)
PASS: ScudoStandalone-Unit :: ./ScudoUnitTest-powerpc64le-Test/107/366 (110231 of 110232)
command timed out: 1200 seconds without output running [b'ninja', b'check-all'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=15568.411116

```

</details>

https://github.com/llvm/llvm-project/pull/195194