Fix null pointer dereference in check_sync_fuzzers

Fix file descriptor leak in get_binary_hash

After c8d1b66 it failed like:

     ===>  Building for afl++-llvm-4.33.c
     [*] Compiling AFL++ for OS FreeBSD on ARCH amd64
     [+] ZLIB detected
     [*] Checking for the default compiler cc...
     [*] Testing the PATH environment variable...
     [*] Checking for the ability to compile x86 code...
     [+] shmat seems to be working.
     [+] Python 3.11.12 support seems to be working.
     [+] Everything seems to be working, ready to compile. (clang version 19.1.7)
     clang19 -O2 -pipe  -fstack-protector-strong -fno-strict-aliasing  -g -Wno-pointer-sign -Wno-variadic-macros -Wall -Wextra -Wno-pointer-arith -fPIC -I include/ -DAFL_PATH=\"/usr/local/afl++-llvm/lib/afl\" -DBIN_PATH=\"/usr/local/afl++-llvm/bin\" -DDOC_PATH=\"/usr/local/afl++-llvm/share/doc/afl\" -I /usr/local/include/ -pthread -flto=full -DHAVE_ZLIB -c src/afl-common.c -o src/afl-common.o
     clang19 -O2 -pipe  -fstack-protector-strong -fno-strict-aliasing  -g -Wno-pointer-sign -Wno-variadic-macros -Wall -Wextra -Wno-pointer-arith -fPIC -I include/ -DAFL_PATH=\"/usr/local/afl++-llvm/lib/afl\" -DBIN_PATH=\"/usr/local/afl++-llvm/bin\" -DDOC_PATH=\"/usr/local/afl++-llvm/share/doc/afl\" -I /usr/local/include/ -pthread -flto=full -DHAVE_ZLIB -c src/afl-sharedmem.c -o src/afl-sharedmem.o
     In file included from src/afl-common.c:28:
     include/forkserver.h:191:3: error: unknown type name 'uid_t'
       191 |   uid_t  uid;
           |   ^
     include/forkserver.h:193:3: error: unknown type name 'pid_t'
       193 |   pid_t  gid;
           |   ^
     include/forkserver.h:195:3: error: unknown type name 'pid_t'
       195 |   pid_t *supl_gids;
           |   ^
     include/forkserver.h:197:3: error: unknown type name 'mode_t'; did you mean '__mode_t'?
       197 |   mode_t perm;
           |   ^~~~~~
           |   __mode_t
     /usr/include/sys/_types.h:127:20: note: '__mode_t' declared here
       127 | typedef __uint16_t      __mode_t;       /* permissions */
           |                         ^
     4 errors generated.
     gmake: *** [GNUmakefile:475: src/afl-common.o] Error 1
     gmake: *** Waiting for unfinished jobs....

Fix the build on FreeBSD

Fix incorrect pointer arithmetic in afl_resize_map_buffers()

…T_BUILD is set

The testing fails in FreeBSD jails if allow.sysvipc isn't set to 1 (default):

    [*] Testing the CC wrapper and instrumentation output...
    unset AFL_USE_ASAN AFL_USE_MSAN AFL_INST_RATIO AFL_LLVM_ALLOWLIST AFL_LLVM_DENYLIST; ASAN_OPTIONS=detect_leaks=0 AFL_QUIET=1 AFL_PATH=. AFL_LLVM_LAF_ALL=1 ./afl-cc -O2 -pipe  -fstack-protector-strong -fno-strict-aliasing  -g -Wno-pointer-sign -Wno-variadic-macros -Wall -Wextra -Wno-pointer-arith -fPIC -I include/ -DAFL_PATH=\"/usr/local/afl++-llvm/lib/afl\" -DBIN_PATH=\"/usr/local/afl++-llvm/bin\" -DDOC_PATH=\"/usr/local/afl++-llvm/share/doc/afl\" -I /usr/local/include/ -pthread -Wall -g -Wno-cast-qual -Wno-variadic-macros -Wno-pointer-sign -I ./include/ -I ./instrumentation/ -DAFL_PATH=\"/usr/local/afl++-llvm/lib/afl\" -DBIN_PATH=\"/usr/local/afl++-llvm/bin\" -DLLVM_BINDIR=\"/usr/local/llvm19/bin\" -DVERSION=\"++4.33c\" -DLLVM_LIBDIR=\"/usr/local/llvm19/lib\" -DLLVM_VERSION=\"19.1.7\" -DAFL_CLANG_FLTO=\"-flto=full\" -DAFL_REAL_LD=\"/usr/local/llvm19/bin/ld.lld\" -DAFL_CLANG_LDPATH=\"1\" -DAFL_CLANG_FUSELD=\"1\" -DCLANG_BIN=\"clang19\" -DCLANGPP_BIN=\"clang++19\" -DUSE_BINDIR=0 -Wno-unused-function -Wno-deprecated  ./test-instr.c -o test-instr  -fstack-protector-strong  -L /usr/local/lib/ -lpthread -lm -lz
    ASAN_OPTIONS=detect_leaks=0 ./afl-showmap -m none -q -o .test-instr0 ./test-instr < /dev/null

    [-]  SYSTEM ERROR : shmget() failed, try running afl-system-config
        Stop location : afl_shm_init(), src/afl-sharedmem.c:303
           OS message : Function not implemented
    gmake[1]: *** [GNUmakefile.llvm:559: test_build] Error 1

Setting AFL_NO_TEST_BUILD=1 allows to build afl++ packages in
poudriere without having to change the jail settings.

Without setting AFL_NO_TEST_BUILD the generated packages are
incomplete:

    fk@test-vm ~/git/privoxy $/usr/local/afl++-llvm/bin/afl-cc --version

    [-] PROGRAM ABORT : Unable to find 'afl-compiler-rt.o'. Please set the AFL_PATH environment variable.
             Location : find_built_deps(), src/afl-cc.c:594

GNUmakefile.llvm: Turn the test_build target into a NOP if AFL_NO_TEST_BUILD is set