v1.4.0

fix: Windows MSYS2 build — pre-run autoreconf in CI step, bump to v1.4.0

Root cause: ExternalProject_Add runs commands via cmake -P / execute_process(),
which creates processes in the Windows/MinGW context, not the MSYS2 context.
This breaks aclocal's MSYS2 path resolution (progtest.m4 not found at the
doubled MSYS2 root path /a/_temp/msys64/usr/share/aclocal/).

Fix: Run autoreconf in a CI workflow step (proper MSYS2 shell context) between
configure and build. ExternalProject only runs ./configure, make, make install.
The autotools invocation (autoreconf/aclocal/automake) is cleanly separated
from the CMake/ExternalProject build.