diff --git a/library/std/build.rs b/library/std/build.rs
index 359ae4f20eea8..f960aa2254e3d 100644
--- a/library/std/build.rs
+++ b/library/std/build.rs
@@ -105,9 +105,6 @@ fn main() {
         ("arm64ec", _) => false,
         // MinGW ABI bugs <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115054>
         ("x86_64", "windows") => false,
-        // Apple has a special ABI for `f16` that we do not yet support
-        // FIXME(builtins): fixed by <https://github.com/rust-lang/compiler-builtins/pull/675>
-        ("x86" | "x86_64", _) if target_vendor == "apple" => false,
         // Missing `__gnu_h2f_ieee` and `__gnu_f2h_ieee`
         ("powerpc" | "powerpc64", _) => false,
         // Missing `__gnu_h2f_ieee` and `__gnu_f2h_ieee`
@@ -116,10 +113,9 @@ fn main() {
         ("riscv32" | "riscv64", _) => false,
         // Most OSs are missing `__extendhfsf` and `__truncsfhf`
         (_, "linux" | "macos") => true,
-        // Almost all OSs besides Linux and MacOS are missing symbols until compiler-builtins can
-        // be updated. <https://github.com/rust-lang/rust/pull/125016> will get some of these, the
-        // next CB update should get the rest.
-        _ => false,
+        // TODO: only for testing, this line will wind up changed as part of
+        // <https://github.com/rust-lang/rust/pull/129385>.
+        _ => true,
     };
 
     let has_reliable_f128 = match (target_arch.as_str(), target_os.as_str()) {