FTBFS on riscv64

As can be seen here [1], the build on riscv64 fails now that we use gcc12 with the following error:

libtool: link: gcc -g -O2 -ffile-prefix-map=/<<PKGBUILDDIR>>=. -fstack-protector-strong -Wformat -Werror=format-security -Werror-implicit-function-declaration -Wno-system-headers -Wl,-Bsymbolic-functions -Wl,-z -Wl,relro -Wl,-z -Wl,now -o .libs/curl slist_wc.o tool_binmode.o tool_bname.o tool_cb_dbg.o tool_cb_hdr.o tool_cb_prg.o tool_cb_rea.o tool_cb_see.o tool_cb_wrt.o tool_cfgable.o tool_dirhie.o tool_doswin.o tool_easysrc.o tool_filetime.o tool_findfile.o tool_formparse.o tool_getparam.o tool_getpass.o tool_help.o tool_helpers.o tool_hugehelp.o tool_libinfo.o tool_listhelp.o tool_main.o tool_msgs.o tool_operate.o tool_operhlp.o tool_panykey.o tool_paramhlp.o tool_parsecfg.o tool_progress.o tool_strdup.o tool_setopt.o tool_sleep.o tool_urlglob.o tool_util.o tool_vms.o tool_writeout.o tool_writeout_json.o tool_xattr.o ../lib/strtoofft.o ../lib/timediff.o ../lib/nonblock.o ../lib/warnless.o ../lib/curl_ctype.o ../lib/curl_multibyte.o ../lib/version_win32.o ../lib/dynbuf.o ../lib/.libs/libcurl.so -lssl -lcrypto -lz
/usr/bin/ld: ../lib/.libs/libcurl.so: undefined reference to `__atomic_exchange_1'
collect2: error: ld returned 1 exit status
make[4]: *** [Makefile:991: curl] Error 1

There exists a bug report and a fix for that upstream here: https://github.com/curl/curl/pull/9061

I'm currently building a package with this patch here [2].

[1] https://launchpadlibrarian.net/612746451/buildlog_ubuntu-kinetic-riscv64.curl_7.84.0-2_BUILDING.txt.gz
[2] https://launchpad.net/~alexghiti/+archive/ubuntu/riscv/+sourcepub/13822857/+listing-archive-extra