Android NDK r26 and utmpx

[Po Lu]

utmpx.h is provided by this new release of the Android NDK, defining
functions as nonfunctional as utmp.h does.

The more pressing problem is that its presence suppresses the definition
of UTMP_NAME_FUNCTION when a program is built with an __ANDROID_API__
lower than 34, where the utmpx* series of functions were introduced,
because the conditional for HAVE_UTMPX_H in readutmp.h does not search
for a `utmpname' function if `utmpxname' is unavailable, with the result
that get_android_boot_time is never invoked.  Here are the relevant
portions of config.log:

configure:9462: checking for utmpx.h
configure:9462: 
/opt/android/ndk/android-ndk-r26/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android22-clang
 -c -O2 -g3 -Werror=implicit-function-declaration  conftest.c >&5
configure:9462: $? = 0
configure:9462: result: yes

configure:16416: 
/opt/android/ndk/android-ndk-r26/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android22-clang
 -o conftest -O2 -g3 -Werror=implicit-function-declaration     conftest.c  >&5 
ld.lld: error: undefined symbol: utmpxname
>>> referenced by conftest.c:116
>>>               /tmp/conftest-c4f4cf.o:(main)
>>> did you mean: utmpname
>>> defined in: 
>>> /opt/android/ndk/android-ndk-r26/toolchains/llvm/prebuilt/linux-x86_64/bin/../sysroot/usr/lib/aarch64-linux-android/22/libc.so

I will install a workaround in Emacs, but it ought to be fixed at the
source.