Aggregate riscv_linux_read_features(int)::__riscv_v_state regs_v has incomplete type and cannot be defined

[Luigi-Crisci]

Hi,
when I try to build the linux toolchain with the vector extension enabled, it complains about type riscv_linux_read_features(int)::__riscv_v_state being incomplete, and then fails to compile.
The newlib build works just fine.
This happens both with v2.8.0 and v2.8.1.
Configured with: ./configure --prefix=$HOME/luigi_crisci/vectorization/compilers/gcc-latest-linux-build --with-arch=rv64imafdc_v0p7_zfh_zvamo0p7_zvlsseg0p7_xtheadc_xtheadba_xtheadbb_xtheadbs_xtheadcmo_xtheadcondmov_xtheadfmemidx_xtheadfmv_xtheadint_xtheadmac_xtheadmemidx_xtheadmempair_xtheadsync --with-abi=lp64d