[zig ld] --gc-sections workaround + tests

`zig cc` emits `--gc-sections` for the linker, which is incompatbile
with what CGo thinks about linking.

This commit adds a workaround: it will add `--no-gc-sections` to the
linking step if the command is not specified (falling back to the
default behavior of gcc/clang).

Related: https://github.com/golang/go/issues/52690

test/gorace/BUILD

@@ -0,0 +1,24 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+load("//rules:rules_go.bzl", "go_binary")
+
+go_library(
+    name = "gorace_lib",
+    srcs = ["main.go"],
+    # keep
+    cgo = True,
+    importpath = "git.sr.ht/~motiejus/bazel-zig-cc/test/gorace",
+    visibility = ["//visibility:private"],
+)
+
+go_binary(
+    name = "gorace",
+    embed = [":gorace_lib"],
+    visibility = ["//visibility:public"],
+)
+
+go_test(
+    name = "gorace_test",
+    srcs = ["main_test.go"],
+    embed = [":gorace_lib"],
+    race = "on",
+)

test/gorace/main.go

@@ -0,0 +1,13 @@
+// Package main tests that Zig can compile race-enabled tests.
+//
+// As of writing, this fails:
+//   CGO_ENABLED=1 CC="zig cc" go test -race .
+//
+// More context: https://github.com/ziglang/zig/issues/11398
+//
+// This fails, because `zig cc` adds `--gc-sections` to the linker
+// flag by default, which is incompatible with cgo. bazel-zig-cc
+// adds a workaround for it.
+package main
+
+func main() {}

test/gorace/main_test.go

@@ -0,0 +1,8 @@
+package main
+
+import "testing"
+
+func TestFoo(t *testing.T) {
+	_ = t
+	main()
+}