Compilation: add missing link file options to cache manifest

Also add a standalone test which covers the `-fentry` case. It does this
by performing two reproducible compilations which are identical other
than having different entry points, and checking whether the emitted
binaries are identical (they should *not* be).

Resolves: #23869

Author: mlugg

src/Compilation.zig

@@ -3233,6 +3233,13 @@ fn addNonIncrementalStuffToCacheManifest(
     man.hash.addOptional(opts.allow_shlib_undefined);
     man.hash.add(opts.bind_global_refs_locally);
 
+    const EntryTag = @typeInfo(link.File.OpenOptions.Entry).@"union".tag_type.?;
+    man.hash.add(@as(EntryTag, opts.entry));
+    switch (opts.entry) {
+        .default, .disabled, .enabled => {},
+        .named => |name| man.hash.addBytes(name),
+    }
+
     // ELF specific stuff
     man.hash.add(opts.z_nodelete);
     man.hash.add(opts.z_notext);
@@ -3254,6 +3261,9 @@ fn addNonIncrementalStuffToCacheManifest(
     man.hash.addOptional(opts.max_memory);
     man.hash.addOptional(opts.global_base);
     man.hash.addListOfBytes(opts.export_symbol_names);
+    man.hash.add(opts.import_symbols);
+    man.hash.add(opts.import_table);
+    man.hash.add(opts.export_table);
 
     // Mach-O specific stuff
     try link.File.MachO.hashAddFrameworks(man, opts.frameworks);
@@ -3264,6 +3274,9 @@ fn addNonIncrementalStuffToCacheManifest(
     man.hash.add(opts.dead_strip_dylibs);
     man.hash.add(opts.force_load_objc);
     man.hash.add(opts.discard_local_symbols);
+    man.hash.addOptional(opts.compatibility_version);
+    man.hash.addOptionalBytes(opts.install_name);
+    man.hash.addOptional(opts.darwin_sdk_layout);
 
     // COFF specific stuff
     man.hash.addOptional(opts.subsystem);
@@ -3272,6 +3285,8 @@ fn addNonIncrementalStuffToCacheManifest(
     man.hash.add(opts.dynamicbase);
     man.hash.addOptional(opts.major_subsystem_version);
     man.hash.addOptional(opts.minor_subsystem_version);
+    man.hash.addOptionalBytes(opts.pdb_source_path);
+    man.hash.addOptionalBytes(opts.module_definition_file);
 }
 
 fn emitFromCObject(

test/standalone/build.zig.zon

@@ -201,6 +201,9 @@
         .config_header = .{
             .path = "config_header",
         },
+        .entry_point = .{
+            .path = "entry_point",
+        },
     },
     .paths = .{
         "build.zig",

test/standalone/entry_point/build.zig

@@ -0,0 +1,46 @@
+pub fn build(b: *std.Build) !void {
+    const mod = b.createModule(.{
+        // Setting the entry point doesn't work properly on all targets right now. Since we're
+        // really just trying to make sure that the compiler *frontend* respects `-fentry` and
+        // includes it in the cache manifest, just test for a target where it works.
+        .target = b.resolveTargetQuery(try .parse(.{
+            .arch_os_abi = "x86_64-linux",
+        })),
+        .optimize = .ReleaseFast, // non-Debug build for reproducible output
+        .root_source_file = b.path("main.zig"),
+    });
+
+    const exe_foo = b.addExecutable(.{
+        .name = "the_exe", // same name for reproducible output
+        .root_module = mod,
+    });
+    exe_foo.entry = .{ .symbol_name = "foo" };
+    const exe_bar = b.addExecutable(.{
+        .name = "the_exe", // same name for reproducible output
+        .root_module = mod,
+    });
+    exe_bar.entry = .{ .symbol_name = "bar" };
+
+    // Despite the output binary being reproducible, the `entry` differed, so the emitted binaries
+    // should be different. But the two compilations are otherwise identical, so if `entry` isn't
+    // being respected properly, we will see identical binaries.
+
+    const check_differ_exe = b.addExecutable(.{
+        .name = "check_differ",
+        .root_module = b.createModule(.{
+            .target = b.graph.host,
+            .optimize = .Debug,
+            .root_source_file = b.path("check_differ.zig"),
+        }),
+    });
+
+    const diff_cmd = b.addRunArtifact(check_differ_exe);
+    diff_cmd.addFileArg(exe_foo.getEmittedBin());
+    diff_cmd.addFileArg(exe_bar.getEmittedBin());
+    diff_cmd.expectExitCode(0);
+
+    const test_step = b.step("test", "Test it");
+    b.default_step = test_step;
+    test_step.dependOn(&diff_cmd.step);
+}
+const std = @import("std");

test/standalone/entry_point/check_differ.zig

@@ -0,0 +1,17 @@
+pub fn main() !void {
+    var arena_state: std.heap.ArenaAllocator = .init(std.heap.page_allocator);
+    defer arena_state.deinit();
+    const arena = arena_state.allocator();
+
+    const args = try std.process.argsAlloc(arena);
+    if (args.len != 3) return error.BadUsage; // usage: 'check_differ <path a> <path b>'
+
+    const contents_1 = try std.fs.cwd().readFileAlloc(arena, args[1], 1024 * 1024 * 64); // 64 MiB ought to be plenty
+    const contents_2 = try std.fs.cwd().readFileAlloc(arena, args[2], 1024 * 1024 * 64); // 64 MiB ought to be plenty
+
+    if (std.mem.eql(u8, contents_1, contents_2)) {
+        return error.FilesMatch;
+    }
+    // success, files differ
+}
+const std = @import("std");

test/standalone/entry_point/main.zig

@@ -0,0 +1,7 @@
+pub const _start = {};
+export fn foo() u32 {
+    return 123;
+}
+export fn bar() u32 {
+    return 456;
+}