[libclc] [libclc][NFC] Add -Wall -Wextra to build flags and fix build warnings (PR #184549)

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``````````bash
git-clang-format --diff origin/main HEAD --extensions cl,inc -- libclc/clc/lib/generic/async/clc_prefetch.inc libclc/clc/lib/generic/math/clc_cosh.inc libclc/clc/lib/generic/math/clc_erfc.cl libclc/clc/lib/generic/math/clc_expm1.inc libclc/clc/lib/generic/math/clc_fmod.cl libclc/clc/lib/generic/math/clc_sincos_helpers_fp64.inc libclc/clc/lib/generic/workitem/clc_get_sub_group_id.cl libclc/clc/lib/ptx-nvidiacl/mem_fence/clc_mem_fence.cl libclc/clc/lib/ptx-nvidiacl/synchronization/clc_work_group_barrier.cl libclc/opencl/lib/generic/async/wait_group_events.cl --diff_from_common_commit
``````````

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``````````diff
diff --git a/libclc/clc/lib/generic/math/clc_fmod.cl b/libclc/clc/lib/generic/math/clc_fmod.cl
index 2aeb0ae5b..d968d007e 100644
--- a/libclc/clc/lib/generic/math/clc_fmod.cl
+++ b/libclc/clc/lib/generic/math/clc_fmod.cl
@@ -130,7 +130,8 @@ _CLC_DEF _CLC_OVERLOAD double __clc_fmod(double x, double y) {
     w *= scale;
   }
 
-  // One more time: final iteration of the subtraction using floor instead of trunc
+  // One more time: final iteration of the subtraction using floor instead of
+  // trunc
   t = __clc_floor(dx / w);
 
   p = w * t;

``````````

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https://github.com/llvm/llvm-project/pull/184549