trunk 20210508 fails to build ada on x86_64-linux-gnux32:

mkdir -p ada/
/<<PKGBUILDDIR>>/build/./prev-gcc/xgcc -B/<<PKGBUILDDIR>>/build/./prev-gcc/ -B/usr/lib/gcc-snapshot/x86_64-linux-gnux32/bin/ -B/usr/lib/
gcc-snapshot/x86_64-linux-gnux32/bin/ -B/usr/lib/gcc-snapshot/x86_64-linux-gnux32/lib/ -isystem /usr/lib/gcc-snapshot/x86_64-linux-gnux3
2/include -isystem /usr/lib/gcc-snapshot/x86_64-linux-gnux32/sys-include   -fchecking=1 -c -g -O2 -fchecking=1  -gnatpg -gnata -W -Wall 
-nostdinc -I- -I. -Iada/generated -Iada -Iada/gcc-interface -I../../src/gcc/ada -I../../src/gcc/ada/gcc-interface -Iada/libgnat -I../../
src/gcc/ada/libgnat ada/einfo-entities.adb -o ada/einfo-entities.o
+===========================GNAT BUG DETECTED==============================+
| 12.0.0 20210508 (experimental) [master revision 292da5c58da:d8763feb89a:62d87a321b29f9febdacc6220367021d98db3057] (x86_64-linux-gnux32
) |
| Assert_Failure nlists.adb:385                                            |
| Error detected at einfo-entities.adb:49:4                                |
| Please submit a bug report; see https://gcc.gnu.org/bugs/ .              |
| Use a subject line meaningful to you and us to track the bug.            |
| Include the entire contents of this bug box in the report.               |
| Include the exact command that you entered.                              |
| Also include sources listed below.                                       |
+==========================================================================+

Please include these source files with error report
Note that list may not be accurate in some cases,
so please double check that the problem can still
be reproduced with the set of files listed.
Consider also -gnatd.n switch (see debug.adb).

../../src/gcc/ada/gcc-interface/system.ads
ada/einfo-entities.adb
ada/generated/einfo-entities.ads
../../src/gcc/ada/einfo.ads
../../src/gcc/ada/namet.ads
../../src/gcc/ada/alloc.ads
../../src/gcc/ada/hostparm.ads
../../src/gcc/ada/types.ads
../../src/gcc/ada/libgnat/unchconv.ads
../../src/gcc/ada/libgnat/unchdeal.ads
../../src/gcc/ada/table.ads
ada/snames.ads
../../src/gcc/ada/stand.ads
../../src/gcc/ada/uintp.ads
../../src/gcc/ada/urealp.ads
ada/generated/seinfo.ads
../../src/gcc/ada/output.ads
../../src/gcc/ada/libgnat/s-os_lib.ads
../../src/gcc/ada/libgnat/s-string.ads
../../src/gcc/ada/libgnat/ada.ads
../../src/gcc/ada/libgnat/a-uncdea.ads
../../src/gcc/ada/sinfo.ads
ada/generated/sinfo-nodes.ads
../../src/gcc/ada/atree.ads
../../src/gcc/ada/einfo-utils.ads
../../src/gcc/ada/libgnat/s-stalib.ads
../../src/gcc/ada/libgnat/a-unccon.ads
../../src/gcc/ada/libgnat/s-exctab.ads
../../src/gcc/ada/libgnat/s-unstyp.ads
../../src/gcc/ada/libgnat/s-conca2.ads
../../src/gcc/ada/libgnat/s-assert.ads
../../src/gcc/ada/gcc-interface/a-assert.ads

compilation abandoned
make[5]: *** [../../src/gcc/ada/gcc-interface/Make-lang.in:139: ada/einfo-entities.o] Error 1
make[5]: *** Waiting for unfinished jobs....
make[5]: Leaving directory '/<<PKGBUILDDIR>>/build/gcc'
make[4]: *** [Makefile:4864: all-stage3-gcc] Error 2
make[4]: Leaving directory '/<<PKGBUILDDIR>>/build'
make[3]: *** [Makefile:27997: stage3-bubble] Error 2
make[3]: Leaving directory '/<<PKGBUILDDIR>>/build'
make[2]: *** [Makefile:28061: bootstrap] Error 2
make[2]: Leaving directory '/<<PKGBUILDDIR>>/build'

Configured with: -v
         --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++
         --prefix=/usr/lib/gcc-snapshot
         --with-gcc-major-version-only
         --program-prefix=
         --enable-shared
         --enable-linker-build-id
         --disable-nls
         --enable-clocale=gnu
         --enable-libstdcxx-debug
         --enable-libstdcxx-time=yes
         --with-default-libstdcxx-abi=new
         --enable-gnu-unique-object
         --disable-vtable-verify
         --enable-plugin
         --with-system-zlib
         --enable-libphobos-checking=release
         --with-target-system-zlib=auto
         --enable-objc-gc=auto
         --enable-multiarch
         --disable-werror
         --enable-cet
         --with-abi=mx32
         --with-multilib-list=mx32,m64,m32
         --enable-multilib
         --enable-checking=yes
         --build=x86_64-linux-gnux32
         --host=x86_64-linux-gnux32
         --target=x86_64-linux-gnux32