GCC 15 error: initializer-string for array of ‘char’ truncates NUL terminator but destination lacks ‘nonstring’ attribute (4 chars into 3 available)

[mkleczek]

Does not build against GCC 15:

gcc -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Wendif-labels -Wmissing-format-attribute -Wimplicit-fallthrough=3 -Wcast-function-type -Wshadow=compatible-local -Wformat-security -Wmissing-variable-declarations -fno-strict-aliasing -fwrapv -fexcess-precision=standard -Wno-format-truncation -Wno-stringop-truncation -O2 -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches -pipe -Wall -Werror=format-security -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -march=x86-64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -mtls-dialect=gnu2 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -std=c11 -Wextra -Wall -Werror -Wno-declaration-after-statement -Wno-vla -Wno-long-long -fPIC -fvisibility=hidden  -DEXTVERSION=\"1.0\" -I. -I./ -I/usr/pgsql-18/include/server -I/usr/pgsql-18/include/internal -D_GNU_SOURCE  -I/usr/include -I/usr/include/libxml2 -DWITH_GZFILEOP     -c -o src/aggs.o src/aggs.c
src/aggs.c:10:22: error: initializer-string for array of ‘char’ truncates NUL terminator but destination lacks ‘nonstring’ attribute (4 chars into 3 available) [-Werror=unterminated-string-initialization]
   10 | const char BOM[3]  = "\xEF\xBB\xBF";
      |                      ^~~~~~~~~~~~~~
cc1: all warnings being treated as errors
make: *** [<builtin>: src/aggs.o] Error 1

Originally posted by @devrimgunduz in #9