Build system: Allow specifying Win32 resource include paths using LazyPath

Adds an `include_paths` field to RcSourceFile that takes a slice of LazyPaths. The paths are resolved and subsequently appended to the -rcflags as `/I <resolved path>`.

This fixes an accidental regression from https://github.com/ziglang/zig/pull/19174. Before that PR, all Win32 resource compilation would inherit the CC flags (via `addCCArgs`), which included things like include directories. After that PR, though, that is no longer the case.

However, this commit intentionally does not restore the previous behavior (inheriting the C include paths). Instead, each .rc file will need to have its include paths specified directly and the include paths only apply to one particular resource script. This allows more fine-grained control and has less potentially surprising behavior (at the cost of some convenience).

Closes #19605

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/std/Build/Module.zig b/lib/std/Build/Module.zig
index d19f0a781e..a142bbd405 100644
--- a/lib/std/Build/Module.zig
+++ b/lib/std/Build/Module.zig
@@ -110,11 +110,18 @@ pub const RcSourceFile = struct {
     ///  /x (ignore the INCLUDE environment variable)
     ///  /D_DEBUG or /DNDEBUG depending on the optimization mode
     flags: []const []const u8 = &.{},
+    /// Include paths that may or may not exist yet and therefore need to be
+    /// specified as a LazyPath. Each path will be appended to the flags
+    /// as `/I <resolved path>`.
+    include_paths: []const LazyPath = &.{},
 
     pub fn dupe(self: RcSourceFile, b: *std.Build) RcSourceFile {
+        const include_paths = b.allocator.alloc(LazyPath, self.include_paths.len) catch @panic("OOM");
+        for (include_paths, self.include_paths) |*dest, lazy_path| dest.* = lazy_path.dupe(b);
         return .{
             .file = self.file.dupe(b),
             .flags = b.dupeStrings(self.flags),
+            .include_paths = include_paths,
         };
     }
 };
@@ -503,6 +510,9 @@ pub fn addWin32ResourceFile(m: *Module, source: RcSourceFile) void {
     rc_source_file.* = source.dupe(b);
     m.link_objects.append(allocator, .{ .win32_resource_file = rc_source_file }) catch @panic("OOM");
     addLazyPathDependenciesOnly(m, source.file);
+    for (source.include_paths) |include_path| {
+        addLazyPathDependenciesOnly(m, include_path);
+    }
 }
 
 pub fn addAssemblyFile(m: *Module, source: LazyPath) void {