$ ./tools/bootstrap_ninja.sh build
+ dir=build
+ mkdir -p build
+ source_filename=samurai-1.2-32-g81cef5d.tar.gz
+ source_url=https://mochiro.moe/wrap/samurai-1.2-32-g81cef5d.tar.gz
+ '[' '!' -d subprojects/samurai ']'
+ c99 -Isubprojects/samurai subprojects/samurai/build.c subprojects/samurai/deps.c subprojects/samurai/env.c subprojects/samurai/graph.c subprojects/samurai/htab.c subprojects/samurai/log.c subprojects/samurai/parse.c subprojects/samurai/samu.c subprojects/samurai/scan.c subprojects/samurai/tool.c subprojects/samurai/tree.c subprojects/samurai/util.c -o build/samu
In file included from /usr/include/errno.h:25,
                 from subprojects/samurai/build.c:5:
/usr/include/features.h:194:3: warning: #warning "_BSD_SOURCE and _SVID_SOURCE are deprecated, use _DEFAULT_SOURCE" [-Wcpp]
  194 | # warning "_BSD_SOURCE and _SVID_SOURCE are deprecated, use _DEFAULT_SOURCE"
      |   ^~~~~~~
/usr/bin/ld: /usr/lib/gcc/x86_64-redhat-linux/12/../../../../lib64/crt1.o: in function `_start':
(.text+0x1b): undefined reference to `main'
collect2: error: ld returned 1 exit status

$ gcc --version
gcc (GCC) 12.2.1 20221121 (Red Hat 12.2.1-4)
$ ld --version 
GNU ld version 2.38-25.fc37