configure: use a native non-cross compiler for linux-user

configure: use a native non-cross compiler for linux-user

Commit c2118e9e1ab ("configure: don't try a "native" cross for linux-user",
2023-11-23) sought to avoid issues with using the native compiler with a
cross-endian or cross-bitness setup.  However, in doing so it ended up
requiring a cross compiler setup (and most likely a slow compiler setup)
even when building TCG tests that are native to the host architecture.
Always allow the host compiler in that case.

Cc: qemu-stable@nongnu.org
Fixes: c2118e9e1ab ("configure: don't try a "native" cross for linux-user", 2023-11-23)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>