This fixes all occurences of `cmake --build` as it already was in one
case with commit HEAD~7.
If omitted, CMake leaves the number of processes used on underlying
implementation, which turns out to `make -j`, thus unlimited number of
cores, which is undesirable.
closes GH-352
It looks like the pre-build library BUILD/Binaries/x64/SpoutLibrary.dll
is no longer compatible with the headers in Git.
Pre-built library version is 2.007.010 while the latest version on GitHub
is Spout 2.007.012. When building Spout from sources, the referenced
issue no longer occurs. Also the libraries are not expected to be included
in the Git in future (leadedge/Spout2#103).
Ensure that /usr/local/{bin,include,lib} are created in scrips that copy
to that.
This is not problem for the CI because `.github/scripts/Windows/prepare_msys.sh`
already creates them but the scripts are standalone installers and it
can be run independently by a developer to install the particular dependency.
