Builds with 'configure' not at the top of srcdir

[Eduardo Hernández]

Hello,

I've been trying to separate the build system and source directory
completely. Part of that would be to have the 'configure' script in the
'build' directory, away from the 'src' directory

The issue is that when I run `./configure --srcdir=../src` the macro
AM_SANITY_CHECK called by AM_INIT_AUTOMAKE tries to figure out if my clock
is fine by using `ls -t "$srcdir/configure" conftest.file` and fails
because configure is not in $srcdir

This is using GNU automake 1.16.5 under MSYS2 in Windows, but the same
happens in an updated Arch Linux

Any tips about how to best handle this?