Analyse following RPM build log snippet. Describe contents accurately, without speculation or suggestions for resolution.            
Your analysis must be as concise as possible, while keeping relevant information intact.
Snippet: 
libtool: compile:  gcc -DPACKAGE_NAME=\"ReadStat\" -DPACKAGE_TARNAME=\"readstat\" -DPACKAGE_VERSION=\"1.1.9\" "-DPACKAGE_STRING=\"ReadStat 1.1.9\"" -DPACKAGE_BUGREPORT=\"https://github.com/WizardMac/ReadStat/issues\" -DPACKAGE_URL=\"https://github.com/WizardMac/ReadStat\" -DPACKAGE=\"readstat\" -DVERSION=\"1.1.9\" -DHAVE_STDIO_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_STRINGS_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_UNISTD_H=1 -DSTDC_HEADERS=1 -DHAVE_DLFCN_H=1 -DLT_OBJDIR=\".libs/\" -DHAVE_ICONV=1 -DICONV_CONST= -I. -g -Wall -Werror -pedantic-errors -std=c99 -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 -c src/spss/readstat_por_write.c  -fPIC -DPIC -o src/spss/.libs/libreadstat_la-readstat_por_write.o
src/spss/readstat_por_write.c: In function 'por_emit_header':
src/spss/readstat_por_write.c:206:5: error: 'strncpy' output may be truncated copying 20 bytes from a string of length 256 [-Werror=stringop-truncation]
  206 |     strncpy(vanity[1] + 20, writer->file_label, 20);
      |     ^
cc1: all warnings being treated as errors
This snippet shows the error which caused the build to fail. The error comes from the gcc command.