Build failure for malloc stuff - amd64 HEAD

[Paul Goyette <paul%whooppee.com@localhost>]

I'm seeing a repeatable error building from sources updated on 
2023-07-04 at 19:12:27 UTC

Here's the details (my mailer will probabl mess it up badly with line
breaks;  for original log see the attachment)

...
dependall ===> lib/libbsdmalloc
#   compile  libbsdmalloc/malloc.go
/build/netbsd-current/tools/x86_64/amd64/bin/x86_64--netbsd-gcc -O2 -fno-builtin-aligned_alloc -fno-builtin-calloc -fno-builtin-free -fno-builtin-malloc -fno-builtin-posix_memalign -fno-builtin-realloc   -std=gnu99    -Wall -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wno-sign-compare  -Wsystem-headers   -Wno-traditional   -Wa,--fatal-warnings  -Wreturn-type -Wswitch -Wshadow -Wcast-qual -Wwrite-strings -Wextra -Wno-unused-parameter -Wno-sign-compare -Werror   -fPIE    --sysroot=/build/netbsd-current/dest/amd64 -D_REENT -D_REENTRANT -I/build/netbsd-current/src_ro/lib/libbsdmalloc/../libc/include/  -c -DDEBUG    -g /build/netbsd-current/src_ro/lib/libbsdmalloc/malloc.c -o malloc.go
/build/netbsd-current/src_ro/lib/libbsdmalloc/malloc.c: In function 'botch':
/build/netbsd-current/src_ro/lib/libbsdmalloc/malloc.c:152:18: error: assignment discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
  152 |  iov[0].iov_base = "\nassertion botched: ";
      |                  ^
/build/netbsd-current/src_ro/lib/libbsdmalloc/malloc.c:154:20: error: cast discards 'const' qualifier from pointer target type [-Werror=cast-qual]
  154 |  iov[1].iov_base = (void *)s;
      |                    ^
/build/netbsd-current/src_ro/lib/libbsdmalloc/malloc.c:156:18: error: assignment discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
  156 |  iov[2].iov_base = "\n";
      |                  ^
cc1: all warnings being treated as errors
*** Failed target: malloc.go
*** Failed commands:
	${_MKTARGET_COMPILE}
	=> @echo '#  ' "compile " libbsdmalloc/malloc.go
	${COMPILE.c} ${DEBUGFLAGS} ${COPTS.${.IMPSRC:T}} ${CPUFLAGS.${.IMPSRC:T}} ${CPPFLAGS.${.IMPSRC:T}} -g ${.IMPSRC} -o ${.TARGET}
	=> /build/netbsd-current/tools/x86_64/amd64/bin/x86_64--netbsd-gcc -O2 -fno-builtin-aligned_alloc -fno-builtin-calloc -fno-builtin-free -fno-builtin-malloc -fno-builtin-posix_memalign -fno-builtin-realloc   -std=gnu99    -Wall -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wno-sign-compare  -Wsystem-headers   -Wno-traditional   -Wa,--fatal-warnings  -Wreturn-type -Wswitch -Wshadow -Wcast-qual -Wwrite-strings -Wextra -Wno-unused-parameter -Wno-sign-compare -Werror   -fPIE    --sysroot=/build/netbsd-current/dest/amd64 -D_REENT -D_REENTRANT -I/build/netbsd-current/src_ro/lib/libbsdmalloc/../libc/include/  -c -DDEBUG    -g /build/netbsd-current/src_ro/lib/libbsdmalloc/malloc.c -o malloc.go
*** [malloc.go] Error code 1
nbmake[7]: stopped in /build/netbsd-current/src_ro/lib/libbsdmalloc
1 error

+--------------------+--------------------------+----------------------+
| Paul Goyette       | PGP Key fingerprint:     | E-mail addresses:    |
| (Retired)          | FA29 0E3B 35AF E8AE 6651 | paul%whooppee.com@localhost    |
| Software Developer | 0786 F758 55DE 53BA 7731 | pgoyette%netbsd.org@localhost  |
| & Network Engineer |                          | pgoyette99%gmail.com@localhost |
+--------------------+--------------------------+----------------------+

...
dependall ===> lib/libbsdmalloc
#   compile  libbsdmalloc/malloc.go
/build/netbsd-current/tools/x86_64/amd64/bin/x86_64--netbsd-gcc -O2 -fno-builtin-aligned_alloc -fno-builtin-calloc -fno-builtin-free -fno-builtin-malloc -fno-builtin-posix_memalign -fno-builtin-realloc   -std=gnu99    -Wall -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wno-sign-compare  -Wsystem-headers   -Wno-traditional   -Wa,--fatal-warnings  -Wreturn-type -Wswitch -Wshadow -Wcast-qual -Wwrite-strings -Wextra -Wno-unused-parameter -Wno-sign-compare -Werror   -fPIE    --sysroot=/build/netbsd-current/dest/amd64 -D_REENT -D_REENTRANT -I/build/netbsd-current/src_ro/lib/libbsdmalloc/../libc/include/  -c -DDEBUG    -g /build/netbsd-current/src_ro/lib/libbsdmalloc/malloc.c -o malloc.go
/build/netbsd-current/src_ro/lib/libbsdmalloc/malloc.c: In function 'botch':
/build/netbsd-current/src_ro/lib/libbsdmalloc/malloc.c:152:18: error: assignment discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
  152 |  iov[0].iov_base = "\nassertion botched: ";
      |                  ^
/build/netbsd-current/src_ro/lib/libbsdmalloc/malloc.c:154:20: error: cast discards 'const' qualifier from pointer target type [-Werror=cast-qual]
  154 |  iov[1].iov_base = (void *)s;
      |                    ^
/build/netbsd-current/src_ro/lib/libbsdmalloc/malloc.c:156:18: error: assignment discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
  156 |  iov[2].iov_base = "\n";
      |                  ^
cc1: all warnings being treated as errors
*** Failed target: malloc.go
*** Failed commands:
	${_MKTARGET_COMPILE}
	=> @echo '#  ' "compile " libbsdmalloc/malloc.go
	${COMPILE.c} ${DEBUGFLAGS} ${COPTS.${.IMPSRC:T}} ${CPUFLAGS.${.IMPSRC:T}} ${CPPFLAGS.${.IMPSRC:T}} -g ${.IMPSRC} -o ${.TARGET}
	=> /build/netbsd-current/tools/x86_64/amd64/bin/x86_64--netbsd-gcc -O2 -fno-builtin-aligned_alloc -fno-builtin-calloc -fno-builtin-free -fno-builtin-malloc -fno-builtin-posix_memalign -fno-builtin-realloc   -std=gnu99    -Wall -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wno-sign-compare  -Wsystem-headers   -Wno-traditional   -Wa,--fatal-warnings  -Wreturn-type -Wswitch -Wshadow -Wcast-qual -Wwrite-strings -Wextra -Wno-unused-parameter -Wno-sign-compare -Werror   -fPIE    --sysroot=/build/netbsd-current/dest/amd64 -D_REENT -D_REENTRANT -I/build/netbsd-current/src_ro/lib/libbsdmalloc/../libc/include/  -c -DDEBUG    -g /build/netbsd-current/src_ro/lib/libbsdmalloc/malloc.c -o malloc.go
*** [malloc.go] Error code 1
nbmake[7]: stopped in /build/netbsd-current/src_ro/lib/libbsdmalloc
1 error