Building world with gcc9 not working

Is building world with gcc still supported? I'm getting an error running
the following:

make XCC=/usr/local/bin/gcc9 XCXX=/usr/local/bin/g++9 buildworld

/usr/local/bin/gcc9 --sysroot=/usr/obj/usr/src/amd64.amd64/tmp
-B/usr/obj/usr/src/amd64.amd64/tmp/usr/bin  -O2 -pipe   -DNO__SCCSID
-DNO__RCSID -I/usr/src/lib/libc/include -I/usr/src/include
-I/usr/src/lib/libc/amd64 -DNLS  -D__DBINTERFACE_PRIVATE
-I/usr/src/contrib/gdtoa -I/usr/src/contrib/libc-vis -DINET6
-I/usr/obj/usr/src/amd64.amd64/lib/libc -I/usr/src/lib/libc/resolv
-D_ACL_PRIVATE -DPOSIX_MISTAKE -I/usr/src/lib/libmd
-I/usr/src/contrib/jemalloc/include -DMALLOC_PRODUCTION
-I/usr/src/contrib/tzcode/stdtime -I/usr/src/lib/libc/stdtime
-I/usr/src/lib/libc/locale -DBROKEN_DES -DPORTMAP -DDES_BUILTIN
-I/usr/src/lib/libc/rpc -DWANT_HYPERV -DYP -DNS_CACHING
-DSYMBOL_VERSIONING -g -MD  -MF.depend.jemalloc_malloc_io.o
-MTjemalloc_malloc_io.o -std=gnu99 -Wno-format-zero-length
-fstack-protector-strong -Wsystem-headers -Werror -Wall -Wno-format-y2k
-Wno-uninitialized -Wno-pointer-sign -Wno-error=address
-Wno-error=array-bounds -Wno-error=attributes -Wno-error=bool-compare
-Wno-error=cast-align -Wno-error=clobbered -Wno-error=enum-compare
-Wno-error=extra -Wno-error=inline -Wno-error=logical-not-parentheses
-Wno-error=strict-aliasing -Wno-error=uninitialized
-Wno-error=unused-but-set-variable -Wno-error=unused-function
-Wno-error=unused-value -Wno-error=misleading-indentation
-Wno-error=nonnull-compare -Wno-error=shift-negative-value
-Wno-error=tautological-compare -Wno-error=unused-const-variable
-Wno-error=bool-operation -Wno-error=deprecated
-Wno-error=expansion-to-defined -Wno-error=format-overflow
-Wno-error=format-truncation -Wno-error=implicit-fallthrough
-Wno-error=int-in-bool-context -Wno-error=memset-elt-size
-Wno-error=noexcept-type -Wno-error=nonnull -Wno-error=pointer-compare
-Wno-error=stringop-overflow -Wno-error=aggressive-loop-optimizations
-Wno-error=cast-function-type -Wno-error=catch-value
-Wno-error=multistatement-macros -Wno-error=restrict
-Wno-error=sizeof-pointer-memaccess -Wno-error=stringop-truncation      
-I/usr/src/lib/libutil -I/usr/src/lib/msun/amd64 -I/usr/src/lib/msun/x86
-I/usr/src/lib/msun/src -c jemalloc_malloc_io.c -o jemalloc_malloc_io.o
jemalloc_malloc_io.c: In function '__je_malloc_vsnprintf':
jemalloc_malloc_io.c:383:2: error: case label value exceeds maximum
value for type [-Werror]
  383 |  case '?' | 0x80:      \
      |  ^~~~
jemalloc_malloc_io.c:595:5: note: in expansion of macro 'GET_ARG_NUMERIC'
  595 |     GET_ARG_NUMERIC(val, 'p');
      |     ^~~~~~~~~~~~~~~
jemalloc_malloc_io.c:401:2: error: case label value exceeds maximum
value for type [-Werror]
  401 |  case 'j' | 0x80:      \
      |  ^~~~
jemalloc_malloc_io.c:595:5: note: in expansion of macro 'GET_ARG_NUMERIC'
  595 |     GET_ARG_NUMERIC(val, 'p');
      |     ^~~~~~~~~~~~~~~
jemalloc_malloc_io.c:389:2: error: case label value exceeds maximum
value for type [-Werror]
  389 |  case 'l' | 0x80:      \
      |  ^~~~
jemalloc_malloc_io.c:595:5: note: in expansion of macro 'GET_ARG_NUMERIC'
  595 |     GET_ARG_NUMERIC(val, 'p');
      |     ^~~~~~~~~~~~~~~
jemalloc_malloc_io.c:395:2: error: case label value exceeds maximum
value for type [-Werror]
  395 |  case 'q' | 0x80:      \
      |  ^~~~
jemalloc_malloc_io.c:595:5: note: in expansion of macro 'GET_ARG_NUMERIC'
  595 |     GET_ARG_NUMERIC(val, 'p');
      |     ^~~~~~~~~~~~~~~
jemalloc_malloc_io.c:410:2: error: case label value exceeds maximum
value for type [-Werror]
  410 |  case 'z' | 0x80:      \
      |  ^~~~
jemalloc_malloc_io.c:595:5: note: in expansion of macro 'GET_ARG_NUMERIC'
  595 |     GET_ARG_NUMERIC(val, 'p');
      |     ^~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
*** Error code 1


-- 
Rebecca Cran