The affected buildroot is:

rhel-10.0-z-flatpak-app-build - https://brewweb.engineering.redhat.com/brew/taginfo?tagID=159022

The same build works fine for the rhel-10.0-firefox-esr-140-stack-build - https://brewweb.engineering.redhat.com/brew/taginfo?tagID=170129

Failed build:
https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=69009220

Failed command: 

2:33.11 process didn't exit successfully: `CARGO=/usr/bin/cargo CARGO_CFG_PANIC=unwind CARGO_CFG_TARGET_ABI='' CARGO_CFG_TARGET_ARCH=s390x CARGO_CFG_TARGET_ENDIAN=big CARGO_CFG_TARGET_ENV=gnu CARGO_CFG_TARGET_FAMILY=unix CARGO_CFG_TARGET_HAS_ATOMIC=128,16,32,64,8,ptr CARGO_CFG_TARGET_OS=linux CARGO_CFG_TARGET_POINTER_WIDTH=64 CARGO_CFG_TARGET_VENDOR=unknown CARGO_CFG_UNIX='' CARGO_ENCODED_RUSTFLAGS='Cdebuginfo=2-cap-lintswarn-Cembed-bitcode=yes-Ccodegen-units=1' CARGO_FEATURE_BINDGEN=1 CARGO_FEATURE_GECKO=1 CARGO_FEATURE_MOZBUILD=1 CARGO_FEATURE_NSSTRING=1 CARGO_FEATURE_REGEX=1 CARGO_FEATURE_SERDE=1 CARGO_FEATURE_TOML=1 CARGO_MANIFEST_DIR=/builddir/build/BUILD/firefox-140.3.0/servo/components/style CARGO_MANIFEST_LINKS=servo_style_crate CARGO_MANIFEST_PATH=/builddir/build/BUILD/firefox-140.3.0/servo/components/style/Cargo.toml CARGO_PKG_AUTHORS='The Servo Project Developers' CARGO_PKG_DESCRIPTION='The Stylo CSS engine' CARGO_PKG_HOMEPAGE='' CARGO_PKG_LICENSE=MPL-2.0 CARGO_PKG_LICENSE_FILE='' CARGO_PKG_NAME=style CARGO_PKG_README=README.md CARGO_PKG_REPOSITORY='https://github.com/servo/stylo' CARGO_PKG_RUST_VERSION='' CARGO_PKG_VERSION=0.0.1 CARGO_PKG_VERSION_MAJOR=0 CARGO_PKG_VERSION_MINOR=0 CARGO_PKG_VERSION_PATCH=1 CARGO_PKG_VERSION_PRE='' DEBUG=false HOST=s390x-unknown-linux-gnu LD_LIBRARY_PATH='/builddir/build/BUILD/firefox-140.3.0/objdir/release/deps:/builddir/build/BUILD/firefox-140.3.0/objdir/release:/usr/lib/rustlib/s390x-unknown-linux-gnu/lib' NUM_JOBS=32 OPT_LEVEL=2 OUT_DIR=/builddir/build/BUILD/firefox-140.3.0/objdir/s390x-unknown-linux-gnu/release/build/style-f4cc5931341896c8/out PROFILE=release RUSTC=/usr/bin/rustc RUSTC_LINKER=/builddir/build/BUILD/firefox-140.3.0/build/cargo-linker RUSTDOC=/usr/bin/rustdoc TARGET=s390x-unknown-linux-gnu /builddir/build/BUILD/firefox-140.3.0/objdir/release/build/style-d7a5342dd968b1d3/build-script-build` (signal: 6, SIGABRT: process abort signal)

 2:33.11   thread 'main' panicked at third_party/rust/bindgen/lib.rs:1091:18:
{{ 2:33.11   we should only write bindings that are valid utf-8: Utf8Error { valid_up_to: 286825, error_len: Some(1) }}}
 2:33.11   stack backtrace:
 2:33.11      0:      0x2aa00606990 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h4bc3f52b0b5a57ee
 2:33.11      1:      0x2aa00641a9a - core::fmt::write::hdc4239539349e6a3
 2:33.11      2:      0x2aa00601d4e - std::io::Write::write_fmt::h0131573bdf4f2f69
 2:33.11      3:      0x2aa00606690 - std::sys::backtrace::BacktraceLock::print::h258237aadeda52a9
 2:33.11      4:      0x2aa00607efe - std::panicking::default_hook::{{closure::h3443f617014cb75e}}
 2:33.11      5:      0x2aa00607d32 - std::panicking::default_hook::h311e6c12debdf3c5
 2:33.11      6:      0x2aa006086e8 - std::panicking::rust_panic_with_hook::h3aeb937654e6e41e
 2:33.11      7:      0x2aa00608402 - std::panicking::begin_panic_handler::{{closure::h15cec0cb36ccba3b}}
 2:33.11      8:      0x2aa006070b4 - std::sys::backtrace::__rust_end_short_backtrace::h795e97a7d9f618a7
 2:33.11      9:      0x2aa00607fda - rust_begin_unwind
 2:33.11     10:      0x2aa0004e2aa - core::panicking::panic_fmt::h3bdab7b46177dc87
 2:33.11     11:      0x2aa0004e74e - core::result::unwrap_failed::h08d62d3da63a11cb
 2:33.11     12:      0x2aa0019d33a - <bindgen::Bindings as core::fmt::Display>::fmt::h05aeccf0037e8da4
 2:33.11     13:      0x2aa00057efa - build_script_build::build_gecko::generate_structs::hf261247f13892132
 2:33.11     14:      0x2aa0005b49c - build_script_build::build_gecko::generate::h47106aff0be72d59
 2:33.11     15:      0x2aa0005f188 - build_script_build::main::hc901cad494b68a58
 2:33.11     16:      0x2aa0005bfbc - std::sys::backtrace::__rust_begin_short_backtrace::h9c39cb77b4b0bed2
 2:33.11     17:      0x2aa0005bf96 - std::rt::lang_start::{{closure::h85a5144e2db21c26}}
 2:33.11     18:      0x2aa005fb696 - std::rt::lang_start_internal::h20c8b7f103a2c218
 2:33.11     19:      0x2aa0005f4c2 - main
 2:33.11     20:      0x3fffdbb437c - __libc_start_call_main
 2:33.11     21:      0x3fffdbb447e - __libc_start_main_impl
 2:33.11     22:      0x2aa0004ea18 - <unknown>
 2:33.11     23:                0x0 - <unknown>
 2:33.11   double free or corruption (fasttop)

Okay build (for rhel-10.0-z): https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=69009317

The buildroots does not differ much, so I'm kind of stumped.

Same build is fine for the flatpak build target and x86_64: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=69009315