Alas, nproc isn't portable (sched_getaffinity() syscall) and

scripts/portability.sh already has two fallbacks (sysctl -n hw.nproc for
mac/bsd and if that doesn't work either it sets CPUS=1).

With this, I built on mac outside of homebrew, albeit cheating to get .config:
$ homebrew
$ make macos_defconfig
$ make clean
$ exit
$ scripts/prereq/build.sh #ignoring SO many warnings
$ mkdir prereq; mv toybox-prereq prereq/
$ for i in $(prereq/toybox-prereq); do ln -s toybox-prereq prereq/$i; done
$ PATH=$PWD/prereq:$PATH scripts/make.sh
$ ./toybox

scripts/prereq/build.sh

@@ -3,13 +3,13 @@
 BUILD='cc -funsigned-char -I scripts/prereq -I . -Os -ffunction-sections -fdata-sections -fno-asynchronous-unwind-tables -fno-strict-aliasing -DTOYBOX_VERSION=""'
 LINK=''
 FILES="
-main.c toys/lsb/gzip.c toys/other/readlink.c toys/other/taskset.c 
-toys/other/which.c toys/pending/tr.c toys/posix/basename.c toys/posix/cat.c 
-toys/posix/chmod.c toys/posix/cmp.c toys/posix/dirname.c toys/posix/echo.c 
-toys/posix/fold.c toys/posix/grep.c toys/posix/head.c toys/posix/ln.c 
-toys/posix/ls.c toys/posix/mkdir.c toys/posix/od.c toys/posix/rm.c 
-toys/posix/sed.c toys/posix/sort.c toys/posix/tail.c toys/posix/tee.c 
-toys/posix/uname.c toys/posix/wc.c toys/posix/xargs.c
+main.c toys/lsb/gzip.c toys/other/readlink.c toys/other/which.c 
+toys/pending/tr.c toys/posix/basename.c toys/posix/cat.c toys/posix/chmod.c 
+toys/posix/cmp.c toys/posix/dirname.c toys/posix/echo.c toys/posix/fold.c 
+toys/posix/grep.c toys/posix/head.c toys/posix/ln.c toys/posix/ls.c 
+toys/posix/mkdir.c toys/posix/od.c toys/posix/rm.c toys/posix/sed.c 
+toys/posix/sort.c toys/posix/tail.c toys/posix/tee.c toys/posix/uname.c 
+toys/posix/wc.c toys/posix/xargs.c
 "
 
 $BUILD lib/*.c $FILES $LINK -o toybox-prereq

scripts/prereq/generated/config.h

@@ -530,8 +530,8 @@
 #define USE_SYSCTL(...)
 #define CFG_TAC 0
 #define USE_TAC(...)
-#define CFG_NPROC 1
-#define USE_NPROC(...) __VA_ARGS__
+#define CFG_NPROC 0
+#define USE_NPROC(...)
 #define CFG_TASKSET 0
 #define USE_TASKSET(...)
 #define CFG_TIMEOUT 0

scripts/prereq/generated/flags.h

@@ -348,16 +348,6 @@
 #undef FLAG_f
 #endif
 
-// taskset   <1^pa
-#undef OPTSTR_taskset
-#define OPTSTR_taskset "<1^pa"
-#ifdef CLEANUP_taskset
-#undef CLEANUP_taskset
-#undef FOR_taskset
-#undef FLAG_a
-#undef FLAG_p
-#endif
-
 // tee ia ia
 #undef OPTSTR_tee
 #define OPTSTR_tee "ia"
@@ -751,15 +741,6 @@
 #define FLAG_f (1LL<<4)
 #endif
 
-#ifdef FOR_taskset
-#define CLEANUP_taskset
-#ifndef TT
-#define TT this.taskset
-#endif
-#define FLAG_a (FORCED_FLAG<<0)
-#define FLAG_p (FORCED_FLAG<<1)
-#endif
-
 #ifdef FOR_tee
 #define CLEANUP_tee
 #ifndef TT
@@ -840,8 +821,6 @@
 #define OPTSTR_gitremote "<1"
 #undef OPTSTR_makedevs
 #define OPTSTR_makedevs "<1>1d:"
-#undef OPTSTR_nproc
-#define OPTSTR_nproc "(all)"
 #undef OPTSTR_toybox
 #define OPTSTR_toybox 0
 #undef OPTSTR_which

scripts/prereq/generated/help.h

@@ -18,7 +18,6 @@
 #define HELP_ls ""
 #define HELP_make ""
 #define HELP_mkdir ""
-#define HELP_nproc ""
 #define HELP_od ""
 #define HELP_readlink ""
 #define HELP_rm ""

scripts/prereq/generated/newtoys.h

@@ -73,7 +73,6 @@ USE_NBD_CLIENT(OLDTOY(nbd-client, nbd_client, TOYFLAG_USR|TOYFLAG_BIN))
 USE_NBD_SERVER(OLDTOY(nbd-server, nbd_server, TOYFLAG_USR|TOYFLAG_BIN))
 USE_NETCAT(OLDTOY(nc, netcat, TOYFLAG_USR|TOYFLAG_BIN))
 USE_NETCAT(NEWTOY(netcat, "^tElLw#<1W#<1p#<1>65535q#<1s:f:46uUnvz[!tlL][!Lw][!Lu][!46U]", TOYFLAG_BIN))
-USE_NPROC(NEWTOY(nproc, "(all)", TOYFLAG_USR|TOYFLAG_BIN))
 USE_OD(NEWTOY(od, "j#vw#<1=16N#xsodcbA:t*", TOYFLAG_USR|TOYFLAG_BIN))
 USE_PASSWD(NEWTOY(passwd, ">1a:dlu", TOYFLAG_STAYROOT|TOYFLAG_USR|TOYFLAG_BIN))
 USE_PASTE(NEWTOY(paste, "d:s", TOYFLAG_USR|TOYFLAG_BIN))

scripts/recreate-prereq.sh

@@ -6,7 +6,7 @@
 
 mkroot/record-commands make clean defconfig toybox
 sed -i 's/default y/default n/' generated/Config.probed
-CMDLIST="$(echo toybox; ./toybox cut -DF 1 log.txt | sort -u)"
+CMDLIST="$(echo toybox; ./toybox cut -DF 1 log.txt | sort -u | grep -v nproc)"
 {
   for i in $(tr '[:lower:]' '[:upper:]' <<<"$CMDLIST")
   do