freetype: improve self-hosted compiler support (use darwin @cImport workaround)

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

libs/freetype/src/c.zig

@@ -1,4 +1,5 @@
-pub usingnamespace @cImport({
+pub usingnamespace if (@import("builtin").zig_backend == .stage1)
+    @cImport({
         @cInclude("hb-ft.h");
         @cInclude("freetype/ftadvanc.h");
         @cInclude("freetype/ftbbox.h");
@@ -8,4 +9,10 @@ pub usingnamespace @cImport({
         @cInclude("freetype/ftsizes.h");
         @cInclude("freetype/ftstroke.h");
         @cInclude("freetype/fttrigon.h");
-});
+    })
+else
+    // TODO(self-hosted): HACK: workaround https://github.com/ziglang/zig/issues/12483
+    //
+    // Extracted from a build using stage1 from zig-cache/ (`cimport.zig`)
+    // Then find+replace `= ?fn` -> `= ?*const fn`
+    @import("cimport1.zig");