Why isn't qemu going?

Question

linux

Termux has dropped support for Android 5.0. You need to build qemu from source. There was a problem building qemu.
At first everything went well, but then there were errors.
Building version 4.2.0

util/mmap-alloc.c:127:13: error: use of undeclared identifier 'MAP_PRIVATE'
    flags = MAP_PRIVATE | MAP_ANONYMOUS;                                                            ^
util/mmap-alloc.c:142:23: error: use of undeclared identifier 'MAP_SHARED'
    flags |= shared ? MAP_SHARED : MAP_PRIVATE;
                      ^
util/mmap-alloc.c:142:36: error: use of undeclared identifier 'MAP_PRIVATE'
    flags |= shared ? MAP_SHARED : MAP_PRIVATE;                                                                            ^
3 errors generated.
make: *** [/data/data/com.termux/files/home/qemu-4.2.0-rc2/rules.mak:69: util/mmap-alloc.o] Error 1
make: *** Waiting for unfinished jobs....
util/memfd.c:133:49: error: use of undeclared identifier 'MAP_SHARED'
    ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
                                                ^
1 error generated.
make: *** [/data/data/com.termux/files/home/qemu-4.2.0-rc2/rules.mak:69: util/memfd.o] Error 1
util/oslib-posix.c:631:13: error: use of undeclared identifier 'MAP_PRIVATE'
    flags = MAP_PRIVATE | MAP_ANONYMOUS;
            ^
1 error generated.

Answer 1

What's incomprehensible? Not connected or simply missing a header containing definitions for MAP_PRIVATE and other identifiers.
manmmap