fast-float: new package (#46137)

* fast-float: new package

* fast-float: add test dependency

* fast-float: fix doctest dependency type

* fast-float: convert deps to tuple

* fast-float: add v6.1.5 and v6.1.6

* fast-float: patch older versions to use find_package(doctest)

var/spack/repos/builtin/packages/fast-float/package.py

@@ -0,0 +1,36 @@
+# Copyright 2013-2024 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+from spack.package import *
+
+
+class FastFloat(CMakePackage):
+    """Fast and exact implementation of the C++ from_chars functions for number
+    types."""
+
+    homepage = "https://github.com/fastfloat/fast_float"
+    url = "https://github.com/fastfloat/fast_float/archive/refs/tags/v6.1.4.tar.gz"
+
+    license("Apache-2.0 OR BSL-1.0 OR MIT", checked_by="pranav-sivararamn")
+
+    version("6.1.6", sha256="4458aae4b0eb55717968edda42987cabf5f7fc737aee8fede87a70035dba9ab0")
+    version("6.1.5", sha256="597126ff5edc3ee59d502c210ded229401a30dafecb96a513135e9719fcad55f")
+    version("6.1.4", sha256="12cb6d250824160ca16bcb9d51f0ca7693d0d10cb444f34f1093bc02acfce704")
+
+    depends_on("cxx", type="build")
+    depends_on("cmake@3.9:", type="build")
+
+    depends_on("doctest", type="test")
+
+    patch(
+        "https://github.com/fastfloat/fast_float/commit/a7ed4e89c7444b5c8585453fc6d015c0efdf8654.patch?full_index=1",
+        sha256="25561aa7db452da458fb0ae3075ef8e63ccab174ca8f5a6c79fb15cb342b3683",
+        when="@:6.1.5",
+    )
+
+    def cmake_args(self):
+        args = [self.define("FASTFLOAT_TEST", self.run_tests), self.define("SYSTEM_DOCTEST", True)]
+
+        return args