[libc][bazel] Add targets for strfrom<float>

Add targets and tests for strfromf, strfromd and strfroml.

No idea why the standard committee decided that the long double function
should be "strfroml" instead of "strfromld" which would match "strtold"
and leave them space to add string from integer functions in future.

Author: michaelrj-google

utils/bazel/llvm-project-overlay/libc/BUILD.bazel

@@ -3571,6 +3571,49 @@ libc_function(
     ],
 )
 
+libc_support_library(
+    name = "str_from_util",
+    hdrs = ["src/stdlib/str_from_util.h"],
+    deps = [
+        ":__support_common",
+        ":__support_cpp_type_traits",
+        ":__support_str_to_integer",
+        ":printf_converter",
+        ":printf_core_structs",
+        ":printf_writer",
+    ],
+)
+
+libc_function(
+    name = "strfromf",
+    srcs = ["src/stdlib/strfromf.cpp"],
+    hdrs = ["src/stdlib/strfromf.h"],
+    deps = [
+        ":__support_common",
+        ":str_from_util",
+    ],
+)
+
+libc_function(
+    name = "strfromd",
+    srcs = ["src/stdlib/strfromd.cpp"],
+    hdrs = ["src/stdlib/strfromd.h"],
+    deps = [
+        ":__support_common",
+        ":str_from_util",
+    ],
+)
+
+libc_function(
+    name = "strfroml",
+    srcs = ["src/stdlib/strfroml.cpp"],
+    hdrs = ["src/stdlib/strfroml.h"],
+    deps = [
+        ":__support_common",
+        ":str_from_util",
+    ],
+)
+
 libc_function(
     name = "strtol",
     srcs = ["src/stdlib/strtol.cpp"],

utils/bazel/llvm-project-overlay/libc/test/src/stdlib/BUILD.bazel

@@ -149,6 +149,37 @@ libc_test(
     deps = ["//libc:types_size_t"],
 )
 
+libc_support_library(
+    name = "strfrom_test_support",
+    hdrs = ["StrfromTest.h"],
+    deps = [
+        "//libc:__support_cpp_type_traits",
+        "//libc:__support_fputil_fp_bits",
+        "//libc/test/UnitTest:LibcUnitTest",
+    ],
+)
+
+libc_test(
+    name = "strfromf_test",
+    srcs = ["strfromf_test.cpp"],
+    libc_function_deps = ["//libc:strfromf"],
+    deps = [":strfrom_test_support"],
+)
+
+libc_test(
+    name = "strfromd_test",
+    srcs = ["strfromd_test.cpp"],
+    libc_function_deps = ["//libc:strfromd"],
+    deps = [":strfrom_test_support"],
+)
+
+libc_test(
+    name = "strfroml_test",
+    srcs = ["strfroml_test.cpp"],
+    libc_function_deps = ["//libc:strfroml"],
+    deps = [":strfrom_test_support"],
+)
+
 libc_support_library(
     name = "strtol_test_helper",
     hdrs = ["StrtolTest.h"],