Disable bindgen layout tests to fix build with newer glibc where struct
sizes (e.g. _IO_FILE) have changed.

--- a/cargo_home/gentoo/ls-qpack-rs-sys-0.3.0/build.rs
+++ b/cargo_home/gentoo/ls-qpack-rs-sys-0.3.0/build.rs
@@ -26,7 +26,7 @@
         .derive_debug(true)
         .derive_default(true)
         .size_t_is_usize(true)
-        .layout_tests(true)
+        .layout_tests(false)
         .generate_comments(false)
         .clang_arg(format!("-I{}", dst.join("include").display()))
         .header(ls_qpack_dir.join("lsqpack.h").to_string_lossy())