Detect tool fails on FreeBSD

[euantorano]

The tools/detect/detect.nim tool fails on FreeBSD with the following output:

``` > nim c -r tools/detect/detect.nim Hint: used config file '/usr/home/euant/src/Nim/config/nim.cfg' [Conf] Hint: used config file '/usr/home/euant/src/Nim/config/config.nims' [Conf] .................. /usr/home/euant/src/Nim/tools/detect/detect.nim(50, 3) Hint: 'ifile' is declared but not used [XDeclaredButNotUsed] CC: detect.nim Hint: [Link] Hint: 44682 lines; 0.861s; 66.336MiB peakmem; Debug build; proj: /usr/home/euant/src/Nim/tools/detect/detect.nim; out: /usr/home/euant/src/Nim/tools/detect/detect [SuccessX] Hint: /usr/home/euant/src/Nim/tools/detect/detect [Exec] CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o testh testh.c sh: gcc: not found Not found: CMD gcc -o genconsts genconsts.c sh: gcc: not found Error: execution of an external program failed: '/usr/home/euant/src/Nim/tools/detect/detect ' ```

Fixing gcc to cc fixes this, but you then get other errors:

``` > nim c -r tools/detect/detect.nim Hint: used config file '/usr/home/euant/src/Nim/config/nim.cfg' [Conf] Hint: used config file '/usr/home/euant/src/Nim/config/config.nims' [Conf] .................. /usr/home/euant/src/Nim/tools/detect/detect.nim(50, 3) Hint: 'ifile' is declared but not used [XDeclaredButNotUsed] CC: detect.nim Hint: [Link] Hint: 44682 lines; 0.860s; 66.336MiB peakmem; Debug build; proj: /usr/home/euant/src/Nim/tools/detect/detect.nim; out: /usr/home/euant/src/Nim/tools/detect/detect [SuccessX] Hint: /usr/home/euant/src/Nim/tools/detect/detect [Exec] CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o testh testh.c Found: CMD cc -o genconsts genconsts.c genconsts.c:472:48: warning: format specifies type 'int' but the argument has type 'const fenv_t *' [-Wformat] fprintf(f, "const FE_DFL_ENV* = cint(%d)\n", FE_DFL_ENV); ~~ ^~~~~~~~~~ /usr/include/fenv.h:99:20: note: expanded from macro 'FE_DFL_ENV' #define FE_DFL_ENV (&__fe_dfl_env) ^~~~~~~~~~~~~~~ genconsts.c:1208:58: warning: format specifies type 'int' but the argument has type '__sighandler_t *' (aka 'void (*)(int)') [-Wformat] fprintf(f, "const SIG_HOLD* = cast[Sighandler](%d)\n", SIG_HOLD); ~~ ^~~~~~~~ /usr/include/sys/signal.h:143:25: note: expanded from macro 'SIG_HOLD' #define SIG_HOLD ((__sighandler_t *)3) ^~~~~~~~~~~~~~~~~~~~~ genconsts.c:1211:57: warning: format specifies type 'int' but the argument has type '__sighandler_t *' (aka 'void (*)(int)') [-Wformat] fprintf(f, "const SIG_DFL* = cast[Sighandler](%d)\n", SIG_DFL); ~~ ^~~~~~~ /usr/include/sys/signal.h:139:18: note: expanded from macro 'SIG_DFL' #define SIG_DFL ((__sighandler_t *)0) ^~~~~~~~~~~~~~~~~~~~~ genconsts.c:1214:57: warning: format specifies type 'int' but the argument has type '__sighandler_t *' (aka 'void (*)(int)') [-Wformat] fprintf(f, "const SIG_ERR* = cast[Sighandler](%d)\n", SIG_ERR); ~~ ^~~~~~~ /usr/include/sys/signal.h:141:18: note: expanded from macro 'SIG_ERR' #define SIG_ERR ((__sighandler_t *)-1) ^~~~~~~~~~~~~~~~~~~~~~ genconsts.c:1217:57: warning: format specifies type 'int' but the argument has type '__sighandler_t *' (aka 'void (*)(int)') [-Wformat] fprintf(f, "const SIG_IGN* = cast[Sighandler](%d)\n", SIG_IGN); ~~ ^~~~~~~ /usr/include/sys/signal.h:140:18: note: expanded from macro 'SIG_IGN' #define SIG_IGN ((__sighandler_t *)1) ^~~~~~~~~~~~~~~~~~~~~ genconsts.c:1230:49: warning: format specifies type 'int' but the argument has type 'key_t' (aka 'long') [-Wformat] fprintf(f, "const IPC_PRIVATE* = cint(%d)\n", IPC_PRIVATE); ~~ ^~~~~~~~~~~ %ld /usr/include/sys/ipc.h:110:21: note: expanded from macro 'IPC_PRIVATE' #define IPC_PRIVATE (key_t)0 /* private key */ ^~~~~~~~ genconsts.c:1582:54: warning: format specifies type 'long' but the argument has type 'int' [-Wformat] fprintf(f, "const CLOCKS_PER_SEC* = clong(%ld)\n", CLOCKS_PER_SEC); ~~~ ^~~~~~~~~~~~~~ %d /usr/include/time.h:59:24: note: expanded from macro 'CLOCKS_PER_SEC' #define CLOCKS_PER_SEC 128 ^~~ 7 warnings generated. ld: error: undefined symbol: __fe_dfl_env >>> referenced by genconsts.c >>> /tmp/genconsts-749663.o:(main) cc: error: linker command failed with exit code 1 (use -v to see invocation) Error: execution of an external program failed: '/usr/home/euant/src/Nim/tools/detect/detect ' ```

Related: #12138