Menuconfig option for musl-libc pretending mmu is just pining for the fijords.

Config.in

@@ -130,4 +130,30 @@ config TOYBOX_UID_USR
 	default 500
 	help
 	  When commands like useradd/groupadd allocate user IDs, start here.
+
+config TOYBOX_MUSL_NOMMU_IS_BROKEN
+	bool "Workaround for musl-libc breakage on nommu systems."
+	default n
+	help
+	  When using musl-libc on a nommu system, you'll need to say "y" here.
+
+	  Although uclibc lets you detect support for things like fork() and
+	  daemon() at compile time, musl intentionally includes broken versions
+	  that always return -ENOSYS on nommu systems, and goes out of its way
+	  to prevent any cross-compile compatible compile-time probes for a
+	  nommu system.
+
+	  Musl does this despite the fact that a nommu system can't even run
+	  standard ELF binaries, and requires specially packaged executables.
+	  (You can't even check a #define to see that you're building against
+	  musl, due to its maintainer's policy that musl never has bugs that
+	  require workarounds.)
+
+	  So our only choice is to manually provide a musl nommu bug workaround
+	  you can manually select to enable (larger, slower) nommu support with
+	  musl.
+
+	  You don't need this for uClibc, we have a compile time probe that
+	  autodetects nommu support there.
+
 endmenu

scripts/genconfig.sh

@@ -89,6 +89,7 @@ EOF
     #include <unistd.h>
     int main(int argc, char *argv[]) { return fork(); }
 EOF
+  echo -e '\tdepends on !TOYBOX_MUSL_NOMMU_IS_BROKEN'
 }
 
 genconfig()