fix([email protected]): support pure = "on"

This switches the `purego` build tag to use the `cgo` tag which
allows the source files to be correctly conditionally included
in the build actions.

There is a second patch that adds a couple of unit tests
that have `pure = "on"` enabled to prevent regressions.

modules/circl/1.3.7.bcr.1/MODULE.bazel

@@ -0,0 +1,16 @@
+module(
+    name = "circl",
+    version = "1.3.7.bcr.1",
+)
+
+bazel_dep(name = "rules_go", version = "0.39.1", repo_name = "io_bazel_rules_go")
+bazel_dep(name = "gazelle", version = "0.31.0")
+
+go_deps = use_extension("@gazelle//:extensions.bzl", "go_deps")
+go_deps.from_file(go_mod = "//:go.mod")
+use_repo(
+    go_deps,
+    "com_github_bwesterb_go_ristretto",
+    "org_golang_x_crypto",
+    "org_golang_x_sys",
+)

modules/circl/1.3.7.bcr.1/patches/add_module_file.patch

@@ -0,0 +1,28 @@
+commit f88c99d4b8d02731ede3fd7e3a5f01fe84336c31
+Author: Fabian Meumertzheim <[email protected]>
+Date:   Tue Jan 9 08:55:10 2024 +0100
+
+    Add MODULE.bazel
+
+diff --git a/MODULE.bazel b/MODULE.bazel
+new file mode 100644
+index 0000000..9754824
+--- /dev/null
++++ b/MODULE.bazel
+@@ -0,0 +1,16 @@
++module(
++    name = "circl",
++    version = "1.3.7.bcr.1",
++)
++
++bazel_dep(name = "rules_go", version = "0.39.1", repo_name = "io_bazel_rules_go")
++bazel_dep(name = "gazelle", version = "0.31.0")
++
++go_deps = use_extension("@gazelle//:extensions.bzl", "go_deps")
++go_deps.from_file(go_mod = "//:go.mod")
++use_repo(
++    go_deps,
++    "com_github_bwesterb_go_ristretto",
++    "org_golang_x_crypto",
++    "org_golang_x_sys",
++)

modules/circl/1.3.7.bcr.1/patches/add_pure_tests_for_mathmatical_libraries.patch

@@ -0,0 +1,59 @@
+From a8c4375a01c55eaef53e457a045e9874fc930d88 Mon Sep 17 00:00:00 2001
+From: Matt Clarkson <[email protected]>
+Date: Fri, 15 Mar 2024 12:10:45 +0000
+Subject: [PATCH] Add pure tests for mathmatical libraries
+
+The libraries have `noasm` support. These tests validate that support does not regress.
+---
+ dh/x25519/BUILD.bazel | 16 ++++++++++++++++
+ dh/x448/BUILD.bazel   | 16 ++++++++++++++++
+ 2 files changed, 32 insertions(+)
+
+diff --git a/dh/x25519/BUILD.bazel b/dh/x25519/BUILD.bazel
+index cacfcf1..7464c66 100644
+--- a/dh/x25519/BUILD.bazel
++++ b/dh/x25519/BUILD.bazel
+@@ -41,3 +41,19 @@ go_test(
+         "//math/fp25519",
+     ],
+ )
++
++go_test(
++    name = "x25519_pure_test",
++    srcs = [
++        "curve_test.go",
++        "key_test.go",
++    ],
++    data = glob(["testdata/**"]),
++    embed = [":x25519"],
++    pure = "on",
++    deps = [
++        "//internal/conv",
++        "//internal/test",
++        "//math/fp25519",
++    ],
++)
+diff --git a/dh/x448/BUILD.bazel b/dh/x448/BUILD.bazel
+index 94a7b2b..b96c160 100644
+--- a/dh/x448/BUILD.bazel
++++ b/dh/x448/BUILD.bazel
+@@ -41,3 +41,19 @@ go_test(
+         "//math/fp448",
+     ],
+ )
++
++go_test(
++    name = "x448_pure_test",
++    srcs = [
++        "curve_test.go",
++        "key_test.go",
++    ],
++    data = glob(["testdata/**"]),
++    embed = [":x448"],
++    pure = "on",
++    deps = [
++        "//internal/conv",
++        "//internal/test",
++        "//math/fp448",
++    ],
++)