wasm2c/spec/float_exprs.txt test fails with GCC 15 on ppc64le and s390x

[rathann]

When building wabt-1.0.36 with GCC 15 (Fedora 42 and rawhide) and running the testsuite on ppc64le

- test/wasm2c/spec/float_exprs.txt
  expected error code 0, got 1.
  STDERR MISMATCH:
  --- expected
  +++ actual
  @@ -0,0 +1,8 @@
  +float_exprs.wast:2238: assertion failed: in w2c_float__exprs__86__wasm_f320x2Eno_trichotomy_lt(&float__exprs__86__wasm_instance, 0.f, make_nan_f32(0x400000)): expected 0, got 1.
  +float_exprs.wast:2239: assertion failed: in w2c_float__exprs__86__wasm_f320x2Eno_trichotomy_le(&float__exprs__86__wasm_instance, 0.f, make_nan_f32(0x400000)): expected 0, got 1.
  +float_exprs.wast:2240: assertion failed: in w2c_float__exprs__86__wasm_f320x2Eno_trichotomy_gt(&float__exprs__86__wasm_instance, 0.f, make_nan_f32(0x400000)): expected 0, got 1.
  +float_exprs.wast:2241: assertion failed: in w2c_float__exprs__86__wasm_f320x2Eno_trichotomy_ge(&float__exprs__86__wasm_instance, 0.f, make_nan_f32(0x400000)): expected 0, got 1.
  +float_exprs.wast:2242: assertion failed: in w2c_float__exprs__86__wasm_f640x2Eno_trichotomy_lt(&float__exprs__86__wasm_instance, 0.0000000000000000, make_nan_f64(0x8000000000000)): expected 0, got 1.
  +float_exprs.wast:2243: assertion failed: in w2c_float__exprs__86__wasm_f640x2Eno_trichotomy_le(&float__exprs__86__wasm_instance, 0.0000000000000000, make_nan_f64(0x8000000000000)): expected 0, got 1.
  +float_exprs.wast:2244: assertion failed: in w2c_float__exprs__86__wasm_f640x2Eno_trichotomy_gt(&float__exprs__86__wasm_instance, 0.0000000000000000, make_nan_f64(0x8000000000000)): expected 0, got 1.
  +float_exprs.wast:2245: assertion failed: in w2c_float__exprs__86__wasm_f640x2Eno_trichotomy_ge(&float__exprs__86__wasm_instance, 0.0000000000000000, make_nan_f64(0x8000000000000)): expected 0, got 1.
  STDOUT MISMATCH:
  --- expected
  +++ actual
  @@ -1 +1 @@
  -794/794 tests passed.
  +786/794 tests passed.

This does not happen with GCC 14.x and is not reproducible on x86_64 or aarch64.