libfuzzer: add standalone test for libfuzzer initialization

test/standalone/build.zig.zon

@@ -108,6 +108,9 @@
         .libcxx = .{
             .path = "libcxx",
         },
+        .libfuzzer = .{
+            .path = "libfuzzer",
+        },
         .load_dynamic_library = .{
             .path = "load_dynamic_library",
         },

test/standalone/libfuzzer/build.zig

@@ -0,0 +1,26 @@
+const std = @import("std");
+const builtin = @import("builtin");
+
+pub fn build(b: *std.Build) void {
+    const target = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{});
+
+    if (builtin.os.tag == .windows) return; // TODO: libfuzzer support for windows
+
+    const run_step = b.step("run", "Run executables");
+    const exe = b.addExecutable(.{
+        .name = "main",
+        .root_module = b.createModule(.{
+            .root_source_file = b.path("main.zig"),
+            .target = target,
+            .optimize = optimize,
+            .fuzz = true,
+        }),
+    });
+
+    b.installArtifact(exe);
+    b.default_step = run_step;
+
+    const run_artifact = b.addRunArtifact(exe);
+    run_step.dependOn(&run_artifact.step);
+}

test/standalone/libfuzzer/main.zig

@@ -0,0 +1,22 @@
+const std = @import("std");
+
+const FuzzerSlice = extern struct {
+    ptr: [*]const u8,
+    len: usize,
+
+    fn fromSlice(s: []const u8) FuzzerSlice {
+        return .{ .ptr = s.ptr, .len = s.len };
+    }
+};
+
+extern fn fuzzer_set_name(name_ptr: [*]const u8, name_len: usize) void;
+extern fn fuzzer_init(cache_dir: FuzzerSlice) void;
+extern fn fuzzer_init_corpus_elem(input_ptr: [*]const u8, input_len: usize) void;
+extern fn fuzzer_coverage_id() u64;
+
+pub fn main() !void {
+    fuzzer_init(FuzzerSlice.fromSlice(""));
+    fuzzer_init_corpus_elem("hello".ptr, "hello".len);
+    fuzzer_set_name("test".ptr, "test".len);
+    _ = fuzzer_coverage_id();
+}