[llvm] [libc][bazel] Add targets for strfrom<float> (PR #128956)

[Alexey Samsonov via llvm-commits]

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@@ -149,6 +149,37 @@ libc_test(
     deps = ["//libc:types_size_t"],
 )
 
+libc_support_library(
+    name = "strfrom_test_support",
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vonosmas wrote:

Similar targets in this file have suffix `_helper`, maybe we should use it here as well?

https://github.com/llvm/llvm-project/pull/128956